mainboard/google/reef: Set PL1 MAX power limit value to 12W

Set PL1 maximum power limit value back to 12W
(https://review.coreboot.org/#/c/16596/)
from 6W due to Intel's and thermal team's suggestion.

BUG=chrome-os-partner:60038
BRANCH=master
TEST=build, boot on electro dut and verify by thermal team member

Change-Id: I57ae29180962724fde72d522caa542f0f21d5922
Signed-off-by: Tim Chen <Tim-Chen@quantatw.com>
Reviewed-on: https://review.coreboot.org/17574
Tested-by: build bot (Jenkins)
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-by: Venkateswarlu V Vinjamuri <venkateswarlu.v.vinjamuri@intel.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/mainboard/google/reef/variants/baseboard/include/baseboard/acpi/dptf.asl

@@ -73,7 +73,7 @@ Name (MPPC, Package ()
 	Package () {	/* Power Limit 1 */
 		0,	/* PowerLimitIndex, 0 for Power Limit 1 */
 		3000,	/* PowerLimitMinimum */
-		6000,	/* PowerLimitMaximum */
+		12000,	/* PowerLimitMaximum */
 		1000,	/* TimeWindowMinimum */
 		1000,	/* TimeWindowMaximum */
 		200	/* StepSize */