mb/google/sarien: Add psys_pmax setting to 136W

This patch adds the setting of psys_pmax to 136W. According to the
design, Rpsys is 11.8Kohm. Here is the equation to come out the
Psys_pmax value: Psys_pmax * 1.493uA/W * 11.8Kohm / 2 = 1.2V
Hence, Psys_pmax is 136W.

BUG=b:124792558
BRANCH=None
TEST=emerge-sarien coreboot chromeos-bootimage & Ensure the value is
     passed to FSP by enabling FSP log & Boot into the OS

Change-Id: Id3f6be5f0c2346a7763195a992c0ae45faede056
Signed-off-by: Gaggery Tsai <gaggery.tsai@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32457
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lijian Zhao <lijian.zhao@intel.com>

src/mainboard/google/sarien/variants/sarien/devicetree.cb

@@ -43,6 +43,7 @@ chip soc/intel/cannonlake
 	register "SlowSlewRateForFivr" = "2"
 	register "tdp_pl1_override" = "15"
 	register "tdp_pl2_override" = "51"
+	register "psys_pmax" = "136"
 	register "Device4Enable" = "1"
 	# Enable eDP device
 	register "DdiPortEdp" = "1"