Re-add xHCI only on haswell and broadwell machines, where
they are needed. Otherwise, keep the same GRUB code.

The xHCI patches were removed because they caused issues
on Sandybridge-based Dell Latitude laptops. See:
https://codeberg.org/libreboot/lbmk/issues/216

The issue was not reported elsewhere, including on the
Haswell/Broadwell hardware where they are needed, but the
build system could only build one version of GRUB.

The older machines do not need xHCI patches, because they
either do not have xHCI patches, or work (in GRUB) because
they're in EHCI mode when running the payload.

So, the problem is that we need the xHCI patches for GRUB
on Haswell/Broadwell hardware, but the patches break
Sandybridge hardware, and we only had the one build of GRUB.
To mitigate this problem, the build system now supports
building multiple revisions of GRUB, with different patches,
and each given coreboot target can say which GRUB tree to use
by setting this in target.cfg:

grubtree="xhci"

In the above example, the "xhci" tree would be used. Some
generic GRUB config has been moved to config/data/grub/
and config/grub/ now looks like config/coreboot/ - also,
the grub.cfg file (named "payload" in each tree) is copied
to the GRUB source tree as ".config", then added to GRUB's
memdisk in the same way, as grub.cfg.

Several other design changes had to be made because of this:

* grub.cfg in memdisk no longer automatically jumps to one
  in CBFS, but now shows a menuentry for it if available

* Certain commands in script/trees are disabled for GRUB,
  such as *config make commands.

* gnulib is now defined in config/submodule/grub/, instead
  of config/git/grub - and this mitigates an existing bug
  where downloading gnulib first would make grub no longer
  possible to download in lbmk.

The coreboot option CONFIG_FINALIZE_USB_ROUTE_XHCI has been
re-enabled on: Dell OptiPlex 9020 MT, Dell OptiPlex 9020 SFF,
Lenovo ThinkPad T440p and Lenovo ThinkPad W541 - now USB should
work again in GRUB.

The GRUB payload has been re-enabled on HP EliteBook 820 G2.

This change will enable per-board GRUB optimisation in the
future. For example, we hardcode what partitions and LVMs
GRUB scans because * is slow on ICH7-based machines, due
to GRUB's design. On other machines, * is reasonably fast,
for automatically enumerating the list of devices for boot.

Use of * (and other wildcards) could enable our GRUB payload
to automatically boot more distros, with minimal fuss. This
can be done at a later date, in subsequent revisions.

Signed-off-by: Leah Rowe <leah@libreboot.org>

Signed-off-by: samuraikid <samuraikid@noreply.codeberg.org>

There is no need to add multiple keymap files, because
GRUB can load keymaps from CBFS. The current build logic
is designed to avoid building multiple GRUB binaries,
which are expensive computationally because each one
would then have to be compressed for each board.

This patch provides the best of both worlds: less space
used in flash like in the old lbmk design (1 keymap per
board), but retaining the current build speeds and therefore
not re-introducing the slowness of lbmk's previous GRUB
build logic.

The grub.cfg file has been modified, accordingly. It now
only loads a keymap.gkb file from CBFS, by default. It does
this, only if that file exists; if not, GRUB already defaults
to US Qwerty layout anyway.

ALSO: compress all keymap gkb files with xz -6

GRUB automatically decompresses files when accessed.
This results in about 2KB of flash space saved in CBFS.

Here is real-world data, showing the increased flash space:

< fallback/payload               0x3eb80    simple elf     548821 none
< keymap.cfg                     0xc4bc0    raw                16 none
< (empty)                        0xc4c00    null         11633316 none
---
> fallback/payload               0x3eb80    simple elf     546787 none
> keymap.gkb                     0xc43c0    raw               344 none
> (empty)                        0xc4540    null         11635044 none

This was taken by diffing the cbfstool "print" output,
both before and after. The *after* result is with this change.
11633316. In this example, 1728 bytes have been saved. Therefore,
with compression taken into account, this patch saves about 1.7KB
of space in CBFS.

This change means that lbmk can now scale to support hundreds
of keymaps, without increasing the amount of flash space used,
in each given image. Since the keymap files are compressed in
lbmk.git, in advance, we spend no additional time on compression
at build time. The resulting change in build speed in negligible.

Adding your own keymap.gkb file was already possible, for changing
the keymap in libreboot images, if you didn't want to change the
memdisk (and thus re-compile grub.elf). Now, this is the default
behaviour, and the only way to do it. It's much more efficient.

The original keymap files can be restored, by running unxz.

Signed-off-by: Leah Rowe <leah@libreboot.org>

Signed-off-by: Leah Rowe <leah@libreboot.org>