x86: ivybridge: Use syscon for the GMA device

Until we have a proper video uclass we can use syscon to handle the GMA
device, and avoid the special device tree and PCI searching. Update the code
to work this way.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/dts/chromebook_link.dts b/arch/x86/dts/chromebook_link.dts
index 662e5d9..d148d6e 100644
--- a/arch/x86/dts/chromebook_link.dts
+++ b/arch/x86/dts/chromebook_link.dts
@@ -209,7 +209,8 @@
 			u-boot,dm-pre-reloc;
 		};
 
-		gma {
+		gma@2,0 {
+			reg = <0x00001000 0 0 0 0>;
 			compatible = "intel,gma";
 			intel,dp_hotplug = <0 0 0x06>;
 			intel,panel-port-select = <1>;