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

see:

https://github.com/9elements/grub/commits/xhci-module-upstreaming-squash_v4/

grub only supports xhci on bios/uefi targets, but not coreboot.
some newer machines don't have ps/2 controllers, and boot in a
way where ehci isn't available at startup; the controller can't
be used by ehci code, there must be xhci support.

the code is from Patrick Rudolph working on behalf of 9elements.
the code was also sent here for review:

https://lists.gnu.org/archive/html/grub-devel/2020-12/msg00111.html

however, upstream never merged these patches. libreboot will have
to maintain these from now on. the patches have been rebased for
use with grub 2.12.

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

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

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

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

this replaces the previous behaviour, which erred
on a specific value of grub_errno, which was a
problem if other types of errors used that value.

due to the way i patch out the prefix error messages,
this new patch ensures that only those errors are
silenced. all other messages will be printed.

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

it still printed "error: ." on screen, instead
of the prefix message.

now it's silent. it just says:

Welcome to GRUB!

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

it can annoy some users, so just silence it. we don't need
a lot of modules so we only have a few, but some distro
grub configs can load modules frivilously.

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

still set grub_errno, and behave the same, but don't
print anything. just carry on execution as normal.

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

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