drm/radeon: make page table updates async v2

Currently doing the update with the CP.

v2: Rebased on Jeromes bugfix. Make validity comparison
    more human readable.

Signed-off-by: Christian König <deathsimple@vodafone.de>
diff --git a/drivers/gpu/drm/radeon/nid.h b/drivers/gpu/drm/radeon/nid.h
index 870db34..2423d1b 100644
--- a/drivers/gpu/drm/radeon/nid.h
+++ b/drivers/gpu/drm/radeon/nid.h
@@ -585,6 +585,7 @@
 #define	PACKET3_SET_CONTEXT_REG_INDIRECT		0x73
 #define	PACKET3_SET_RESOURCE_INDIRECT			0x74
 #define	PACKET3_SET_APPEND_CNT			        0x75
+#define	PACKET3_ME_WRITE				0x7A
 
 #endif