mb/google/poppy: Add support for ACPI brightness controls

Change-Id: Ie7eb4c43178acff2dc5ff7c685e71990d8f353c9
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39945
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/src/mainboard/google/poppy/variants/atlas/devicetree.cb b/src/mainboard/google/poppy/variants/atlas/devicetree.cb
index 52a2dc7..b7ab523 100644
--- a/src/mainboard/google/poppy/variants/atlas/devicetree.cb
+++ b/src/mainboard/google/poppy/variants/atlas/devicetree.cb
@@ -1,5 +1,8 @@
 chip soc/intel/skylake
 
+	# IGD Displays
+	register "gfx" = "GMA_STATIC_DISPLAYS(0)"
+
 	register "gpu_pp_up_delay_ms"		  = "200"
 	register "gpu_pp_down_delay_ms"		  = "50"
 	register "gpu_pp_cycle_delay_ms"	  = "600"