drm/radeon: Handle DP_AUX_I2C_WRITE_STATUS_UPDATE

When we get an i2c defer or short ack for i2c-over-aux write we need
to switch to WRITE_STATUS_UPDATE to poll for the completion of the
original request.

Looks like radeon doesn't do anything special with the request type,
so hopefully just treating it the same as a i2c write is enough.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/radeon/atombios_dp.c

@@ -179,6 +179,7 @@ radeon_dp_aux_transfer_atom(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 	switch (msg->request & ~DP_AUX_I2C_MOT) {
 	case DP_AUX_NATIVE_WRITE:
 	case DP_AUX_I2C_WRITE:
+	case DP_AUX_I2C_WRITE_STATUS_UPDATE:
 		/* The atom implementation only supports writes with a max payload of
 		 * 12 bytes since it uses 4 bits for the total count (header + payload)
 		 * in the parameter space.  The atom interface supports 16 byte