vendorcode/google: consolidate strong mainboard_get_dram_part_num routines

Move mainboard_get_dram_part_num() into common location in
vendorcode/google/chromeos/dram_part_num_override.c.

Change mainboard_get_dram_part_num() to take no input parameters and to
return a pointer to a null-terminated string if override name is found.

Remove strong declarations of mainboard_get_dram_part_num in lieu of new
common version.

Enable CHROMEOS_DRAM_PART_NUMBER_IN_CBI for hatch, volteer, and dedede.

BUG=b:168724473
TEST="emerge-volteer coreboot chromeos-bootimage" and verify it
builds sucessfully,

Change-Id: I49b7b2be7b46b5ffd6377d6caabd5e3e6c0a8d61
Signed-off-by: Nick Vaccaro <nvaccaro@google.com>
---
M src/include/memory_info.h
M src/lib/spd_bin.c
M src/mainboard/google/dedede/Kconfig
M src/mainboard/google/dedede/romstage.c
M src/mainboard/google/hatch/Kconfig
M src/mainboard/google/hatch/romstage_spd_cbfs.c
M src/mainboard/google/volteer/Kconfig
M src/mainboard/google/volteer/romstage.c
M src/soc/intel/alderlake/romstage/romstage.c
M src/soc/intel/cannonlake/romstage/romstage.c
M src/soc/intel/elkhartlake/romstage/romstage.c
M src/soc/intel/jasperlake/romstage/romstage.c
M src/soc/intel/tigerlake/romstage/romstage.c
M src/vendorcode/google/chromeos/Makefile.inc
A src/vendorcode/google/chromeos/dram_part_num_override.c
15 files changed, 60 insertions(+), 89 deletions(-)