drm/amdgpu/gfx11: select HDP ref/mask according to gfx ring pipe

Use correct ref/mask for differnent gfx ring pipe. Ported from
ZhenGuo's patch for gfx10.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c

@@ -5491,7 +5491,7 @@ static void gfx_v11_0_ring_emit_hdp_flush(struct amdgpu_ring *ring)
 		}
 		reg_mem_engine = 0;
 	} else {
-		ref_and_mask = nbio_hf_reg->ref_and_mask_cp0;
+		ref_and_mask = nbio_hf_reg->ref_and_mask_cp0 << ring->pipe;
 		reg_mem_engine = 1; /* pfp */
 	}