mainboard/google/meowth: enable PCH iSCLK

Turn on PCH iSCLK for meowth platform.

BUG=None
TEST=Boot up into OS and check register programming with iotools, the
command is iotools mmio_read32 0xfdad8000, returned value is 0x03.

Change-Id: I1e44e3748c9b37c8f60adcc47a866d445d77cfaa
Signed-off-by: Lijian Zhao <lijian.zhao@intel.com>
Reviewed-on: https://review.coreboot.org/23368
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/zoombini/variants/meowth/devicetree.cb

@@ -53,6 +53,9 @@ chip soc/intel/cannonlake
 	register "usb3_ports[0]" = "USB3_PORT_DEFAULT(OC2)"
 	register "usb3_ports[1]" = "USB3_PORT_DEFAULT(OC3)"
 
+	# Enable Pch iSCLK
+	register "pch_isclk" = "1"
+
 	# Touchscreen Digitizer
 	register "i2c[0]" = "{
 		.speed = I2C_SPEED_FAST_PLUS,