Add PMC IPC commands information for FIVR control functionality
BUG=b:198582766
BRANCH=None
TEST=Build FW and test on brya0 board
Change-Id: I9d08bb71f7ea5da7614c68fc0ce4edf9aef59baa
Signed-off-by: Sumeet Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57922
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>