also bring the coreboot/next modules in line with
the recent merge that did away with coreboot/dell7

the submodules for coreboot/haswell were still there,
and have now been deleted; the haswell tree was used
for the NRI patches, which were moved to /default some
time ago

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

Specifically, use the same revision that Mate used in patchset 15.

This will ensure that any issues are *not* caused by the coreboot
revision; this is being done, because the old coreboot revision was
from July, but patchset 15 from Mate is based on a September revision
of coreboot.

I've been eliminating as many variables as possible, trying to fix
SeaBIOS payload on this machine, because it hangs in Libreboot, but
not when building from gerrit directly, which means the coreboot
revision may be a factor (since I'm using his patches on an older
revision so upstream might have made some changes since then that
the port relies on).

For this, a new coreboot tree is used, called "dell7", referring to
the fact that Kabylake is Intel's 7th generation.

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