drm/radeon/kms: add HDP flushing for all GPUs.

rendercheck under kms on r600s was failing due to HDP flushing not happening.

This adds HDP flushing to the object wait function for r100->r700 families.

rendercheck passes basic tests on r600 with this change.

Acked-by: Alex Deucher <alexdeucher@gmail.com>
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 278f646..797a36f 100644
--- a/drivers/gpu/drm/radeon/r600.c
+++ b/drivers/gpu/drm/radeon/r600.c
@@ -1101,6 +1101,10 @@
 	(void)RREG32(PCIE_PORT_DATA);
 }
 
+void r600_hdp_flush(struct radeon_device *rdev)
+{
+	WREG32(R_005480_HDP_MEM_COHERENCY_FLUSH_CNTL, 0x1);
+}
 
 /*
  * CP & Ring