drm/radeon/kms/evergreen: fix gpu hangs in userspace accel code

These VGT regs need to be programmed via the ring rather than
MMIO as on previous asics (r6xx/r7xx).

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/r600.c b/drivers/gpu/drm/radeon/r600.c
index 04f134d..afc18d8 100644
--- a/drivers/gpu/drm/radeon/r600.c
+++ b/drivers/gpu/drm/radeon/r600.c
@@ -2119,10 +2119,7 @@
 	}
 	radeon_ring_write(rdev, PACKET3(PACKET3_ME_INITIALIZE, 5));
 	radeon_ring_write(rdev, 0x1);
-	if (rdev->family >= CHIP_CEDAR) {
-		radeon_ring_write(rdev, 0x0);
-		radeon_ring_write(rdev, rdev->config.evergreen.max_hw_contexts - 1);
-	} else if (rdev->family >= CHIP_RV770) {
+	if (rdev->family >= CHIP_RV770) {
 		radeon_ring_write(rdev, 0x0);
 		radeon_ring_write(rdev, rdev->config.rv770.max_hw_contexts - 1);
 	} else {