mb/google/rex/var/screebo: Set TCC to 90°C

Set tcc_offset value to 20 in devicetree for Thermal Control Circuit
(TCC) activation feature for proto phase.

BUG=b:282865187
BRANCH=None
TEST=Build FW and test on Screebo board

Change-Id: I3a929aa20a700376d2a0a150911fed34e67f78eb
Signed-off-by: Wentao Qin <qinwentao@huaqin.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75360
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Haikun Zhou <zhouhaikun5@huaqin.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/rex/variants/screebo/overridetree.cb

@@ -50,6 +50,9 @@ chip soc/intel/meteorlake
 		[PchSerialIoIndexI2C5] = PchSerialIoPci,
 	}"
 
+	# Temporary setting TCC of 90C = Tj max - Tcc
+	register "tcc_offset" = "20"
+
 	# Intel Common SoC Config
 	#+-------------------+---------------------------+
 	#| Field             |  Value                    |