mb/google/auron: Refactor memory-down SPD handling
Variants only need to provide the SPD index and whether said index
corresponds to a dual-channel configuration, which can be achieved
without using `pei_data`. Add two functions that return the values
and use them in `spd.c` at mainboard level.
Change-Id: I9bc4527057d4a771883c8cc60da2501516d6fb94
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55803
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>