mb/google/brya: Create rull variant

mb/google/brya: Create rull variant

Create the rull variant of the nissa reference board by copying
the template files to a new directory named for the variant.
And based on schematics NB7559_MB_SCH_V1_2024_1010.pdf
update devicetree settings.

(Auto-Generated by create_coreboot_variant.sh version 4.5.0)

BUG=b:374673463
BRANCH=None
TEST=util/abuild/abuild -p none -t google/brya -x -a
make sure the build includes GOOGLE_RULL

Change-Id: If48273f3e9db69507b41ea0313916d94ecabe309
Signed-off-by: Rui Zhou <zhourui@huaqin.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/84828
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Eric Lai <ericllai@google.com>