x86: Add initial video device init for Intel GMA

Intel's Graphics Media Accelerator (GMA) is a generic name for a wide range
of video devices. Add code to set up the hardware on ivybridge. Part of the
init happens in native code, part of it happens in a 16-bit option ROM for
those nostalgic for the 1970s.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/fdtdec.h

@@ -122,6 +122,7 @@ enum fdt_compat_id {
 	COMPAT_MEMORY_SPD,		/* Memory SPD information */
 	COMPAT_INTEL_PANTHERPOINT_AHCI,	/* Intel Pantherpoint AHCI */
 	COMPAT_INTEL_MODEL_206AX,	/* Intel Model 206AX CPU */
+	COMPAT_INTEL_GMA,		/* Intel Graphics Media Accelerator */
 
 	COMPAT_COUNT,
 };