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

Create common Intel systemagent code.
This code currently contains the SA initialization
required in Bootblock phase, which has the following programming-
* Set PCIEXBAR
* Clear TSEG register
More code will get added up in the subsequent phases.

Change-Id: I6f0c515278f7fd04d407463a1eeb25ba13639f5c
Signed-off-by: Barnali Sarkar <barnali.sarkar@intel.com>
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/18565
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
4 files changed