soc/intel: Make use of PMC low power program from common block

soc/intel: Make use of PMC low power program from common block

List of changes:
1. Select PMC_LOW_POWER_MODE_PROGRAM from applicable SoC directory
2. Remove redundant PMC programming from SoC and refer to common
code block
3. Remove unused 'reg8' and 'reg32' variable as applicable from SoC
function.

Change-Id: I18894c49cfc6e88675b5fb71bca0412e5639fb4b
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45796
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>