r600g: don't use r600_context_reg on evergreen

Just getting rid of things which use the register mask.

Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/src/gallium/drivers/r600/r600_hw_context_priv.h b/src/gallium/drivers/r600/r600_hw_context_priv.h
index 2ad5624..c7d5b6a 100644
--- a/src/gallium/drivers/r600/r600_hw_context_priv.h
+++ b/src/gallium/drivers/r600/r600_hw_context_priv.h
@@ -30,7 +30,7 @@
 #include "util/u_hash_table.h"
 #include "os/os_thread.h"
 
-#define R600_MAX_DRAW_CS_DWORDS 11
+#define R600_MAX_DRAW_CS_DWORDS 17
 
 #define PKT_COUNT_C                     0xC000FFFF
 #define PKT_COUNT_S(x)                  (((x) & 0x3FFF) << 16)