mb/google/brya: Migrate brya to use SPD files under spd/

mb/google/brya: Migrate brya to use SPD files under spd/

SPD files are being moved from the soc and mainboard directories to a
centralised spd/ directory. This change migrates all brya variants to
use this new location. The contents of the new SPDs are identical, only
their file paths have changed.

The variant Makefile.inc and dram_id.generated.txt files were generated
using the part_id_gen tool. E.g. for anahera:

util/spd_tools/bin/part_id_gen \
  ADL \
  lp4x \
  src/mainboard/google/brya/variants/anahera/memory \
  src/mainboard/google/brya/variants/anahera/memory/mem_parts_used.txt

BUG=b:191776301
TEST=Check that each variant's coreboot.rom is the same with and without
this change. Built using: abuild -p none -t google/brya -a -x --timeless

Change-Id: I08efe1d75438c81161d9b496af2fa30ce6f59ade
Signed-off-by: Reka Norman <rekanorman@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57661
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>