soc/intel/common/block: Add Intel PMC support

soc/intel/common/block: Add Intel PMC support

PMC util code is very similar accross different intel SOC's.
This patch is an effort to move those code in common place
so that it can be shared accross different intel platforms
instead of duplicating for each platform. This patch adds
pmclib.c file which contains the pmc utility functions
common accross SOC's. The config for common PMC is
SOC_INTEL_COMMON_BLOCK_PMC which can be defined in SOC's
Kconfig file in order to use the common PMC util code.

Change-Id: Ic3d96fc23a98c30e8ea0969a7be09d217eeaa889
Signed-off-by: Shaunak Saha <shaunak.saha@intel.com>
Reviewed-on: https://review.coreboot.org/19349
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>