drm/radeon: re-enable PTE/PDE packet for set_page on cayman/TN

PTE/PDE doesn't support a single update (count = 1).  We had
previously disabled it since it we were hitting that case which
let to hangs.  The PTE/PDE packet is much more efficient for VM
updates where it can be used.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/nid.h

@@ -684,6 +684,11 @@
 					 (((vmid) & 0xF) << 20) |	\
 					 (((n) & 0xFFFFF) << 0))
 
+#define DMA_PTE_PDE_PACKET(n)		((2 << 28) |			\
+					 (1 << 26) |			\
+					 (1 << 21) |			\
+					 (((n) & 0xFFFFF) << 0))
+
 /* async DMA Packet types */
 #define	DMA_PACKET_WRITE				  0x2
 #define	DMA_PACKET_COPY					  0x3