mb/starlabs/starbook/tgl: Enable P2SB

Enable the P2SB so that the SPI is discoverable by the OS.

Change-Id: I49802f93a97a18ecc10f48d213619855728e1290
Signed-off-by: Sean Rhodes <sean@starlabs.systems>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67029
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/starlabs/starbook/variants/tgl/devicetree.cb

@@ -181,6 +181,7 @@ chip soc/intel/tigerlake
 				device pnp 4e.19 off end			# Power Management Channel 5
 			end
 		end
+		device ref p2sb		on  end
 		device ref pmc		hidden end
 		device ref hda		on
 			register "PchHdaAudioLinkHdaEnable"	= "1"