soc/intel/alderlake: Add provision to override Rcomp settings

soc/intel/alderlake: Add provision to override Rcomp settings

Add function to allow overriding the RcompResistor and
RcompTarget UPDs from mainboard if required.

Mainboard users can pass required rcomp from memory.c file.

Refactor ddr_config structure to take out rcomp related variable
outside for all memory type to override if required.

BUG=b:182772421
TEST=Able to override the default RcompResistor and RcompTarget
values.

Change-Id: Ie8528bbf0517728534d47f9adaabfc9a2c469609
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51683
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>