Change in coreboot[master]: mb/google/rex: Add memory init

[Subrata Banik (Code Review)]

Attention is currently required from: Tarun Tuli, Tim Wawrzynczak, Kapil Porwal, Eric Lai.
Subrata Banik has uploaded a new patch set (#4) to the change originally created by Eric Lai. ( https://review.coreboot.org/c/coreboot/+/64850 )

Change subject: mb/google/rex: Add memory init
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mb/google/rex: Add memory init

Add memory init with placeholder. DQ map can be auto probed by fsp.
So leave it as default.

BUG=b:224325352
TEST=util/abuild/abuild -p none -t google/rex -a -c max
Able to boot till FSP-M/MRC using MTL simics.

Signed-off-by: Eric Lai 
Signed-off-by: Subrata Banik 
Change-Id: I5baa87411c28a20602eb5a7077f00664ccab3ade
---
M src/mainboard/google/rex/Kconfig
M src/mainboard/google/rex/Makefile.inc
M src/mainboard/google/rex/romstage.c
A src/mainboard/google/rex/spd/Makefile.inc
M src/mainboard/google/rex/variants/baseboard/include/baseboard/variants.h
M src/mainboard/google/rex/variants/baseboard/rex/Makefile.inc
A src/mainboard/google/rex/variants/baseboard/rex/memory.c
A src/mainboard/google/rex/variants/rex0/memory/Makefile.inc
A src/mainboard/google/rex/variants/rex0/memory/dram_id.generated.txt
A src/mainboard/google/rex/variants/rex0/memory/mem_parts_used.txt
10 files changed, 84 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/50/64850/4