igd.asl rewrite

Old igd.asl had inconsistent addresses (between _DOD and actual device)
and ghost devices. Any of those is enough to make brightness on windows
fail and make igd.asl out-of-ACPI-spec. Also old code favoured ridiculous
copying of the same thing 6 times per chipset. Leave only hooking up and
chipset-specific part in chipset directory. Move NVS handling and ACPI-spec
parts to a common file.

Change-Id: I556769e5e28b83e7465e3db689e26c8c0ab44757
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/7472
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <edward.ocallaghan@koparo.com>
Reviewed-by: Timothy Pearson <tpearson@raptorengineeringinc.com>
diff --git a/src/mainboard/apple/macbook21/devicetree.cb b/src/mainboard/apple/macbook21/devicetree.cb
index e70ca05..0430217 100644
--- a/src/mainboard/apple/macbook21/devicetree.cb
+++ b/src/mainboard/apple/macbook21/devicetree.cb
@@ -20,11 +20,14 @@
 ##
 
 chip northbridge/intel/i945
+	# IGD Displays
+	register "gfx.ndid" = "3"
+	register "gfx.did" = "{ 0x80000100, 0x80000240, 0x80000410, 0x80000410, 0x00000005 }"
 
 	register "gpu_hotplug" = "0x00000220"
 	register "gpu_lvds_use_spread_spectrum_clock" = "1"
 	register "gpu_lvds_is_dual_channel" = "0"
-	register "gpu_backlight" = "0x1280128"
+	register "gpu_backlight" = "0x1290128"
 
 	device cpu_cluster 0 on
 		chip cpu/intel/socket_mFCPGA478