mb/google/caroline: Re-enable I2C2 / fix digitizer

Caroline has a Wacom W9013 digitizer on I2C2, which was
incorrectly disabled in commit d957d12e6
[mb/google/glados: clean up variant devicetrees]
as part of preparation for converting to overridetree format.

Test: build/boot, verify digitizer now available under Linux

Change-Id: I234bc0126b5d13c22a663d6544382890b312ce63
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51507
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/src/mainboard/google/glados/variants/caroline/overridetree.cb b/src/mainboard/google/glados/variants/caroline/overridetree.cb
index e213d02..6f55dce 100644
--- a/src/mainboard/google/glados/variants/caroline/overridetree.cb
+++ b/src/mainboard/google/glados/variants/caroline/overridetree.cb
@@ -17,6 +17,15 @@
 	register "usb3_ports[0]" = "USB3_PORT_DEFAULT(OC_SKIP)" # Type-C Port (main)
 	register "usb3_ports[1]" = "USB3_PORT_DEFAULT(OC_SKIP)" # Type-C Port (sub)
 
+	register "SerialIoDevMode" = "{
+		[PchSerialIoIndexI2C0]  = PchSerialIoPci,	// touchpad
+		[PchSerialIoIndexI2C1]  = PchSerialIoPci,	// touchscreen
+		[PchSerialIoIndexI2C2]  = PchSerialIoPci,	// digitizer
+		[PchSerialIoIndexI2C4]  = PchSerialIoPci,	// audio
+		[PchSerialIoIndexUart0] = PchSerialIoPci,
+		[PchSerialIoIndexUart2] = PchSerialIoSkipInit,
+	}"
+
 	# PL2 override 15W
 	register "power_limits_config" = "{
 		.tdp_pl2_override = 15,