drm/vgaarb: add VGA arbitration support to the drm and kms.

VGA arb requires DRM support for non-kms drivers, to turn on/off
irqs when disabling the mem/io regions.

VGA arb requires KMS support for GPUs where we can turn off VGA
decoding. Currently we know how to do this for intel and radeon
kms drivers, which allows them to be removed from the arbiter.

This patch comes from Fedora rawhide kernel.

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/r600d.h b/drivers/gpu/drm/radeon/r600d.h
index 723295f..4a9028a 100644
--- a/drivers/gpu/drm/radeon/r600d.h
+++ b/drivers/gpu/drm/radeon/r600d.h
@@ -78,6 +78,7 @@
 #define CB_COLOR0_MASK                                  0x28100
 
 #define	CONFIG_MEMSIZE					0x5428
+#define CONFIG_CNTL					0x5424
 #define	CP_STAT						0x8680
 #define	CP_COHER_BASE					0x85F8
 #define	CP_DEBUG					0xC1FC