mb/google/guybrush: Enable internal graphics

BUG=b:181809122
TEST=builds

Signed-off-by: Mathew King <mathewk@chromium.org>
Change-Id: I64475a475e9b72a6edd04ce0728591e0649d9f60
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51244
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/mainboard/google/guybrush/variants/baseboard/devicetree.cb

@@ -39,5 +39,8 @@ chip soc/amd/cezanne
 	}"
 
 	device domain 0 on
+		device ref gpp_bridge_a on  # Internal GPP Bridge 0 to Bus A
+			device ref gfx on end # Internal GPU (GFX)
+		end
 	end # domain
 end	# chip soc/amd/cezanne