mb/google/caroline: Enable I2C #2 in devicetree

Commit 98ec53bdf1 (mb/google/caroline:
Re-enable I2C2 / fix digitizer) enabled I2C #2 in the `SerialIoDevMode`
array, but left the device disabled in the devicetree. Enable it.

Change-Id: I67eec1c753bfd2a78ed0c1e0a78057cd4a3d4153
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57224
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>

src/mainboard/google/glados/variants/caroline/overridetree.cb

@@ -55,6 +55,7 @@ chip soc/intel/skylake
 				device i2c 4a on end
 			end
 		end # I2C #1
+		device pci 15.2 on  end # I2C #2
 		device pci 19.2 on
 			chip drivers/i2c/nau8825
 				register "irq" = "ACPI_IRQ_LEVEL_LOW(GPP_F10_IRQ)"