sfc: Reduce log level for MCDI error response in efx_mcdi_rpc()

Some errors are expected, e.g. when sending new commands to an MC
running old firmware.  Only the caller of efx_mcdi_rpc() can decide
what is a real error.  Therefore log the error responses with
netif_dbg().
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/sfc/mcdi.c

@@ -381,7 +381,7 @@ int efx_mcdi_rpc(struct efx_nic *efx, unsigned cmd,
 				  -rc);
 			efx_schedule_reset(efx, RESET_TYPE_MC_FAILURE);
 		} else
-			netif_err(efx, hw, efx->net_dev,
+			netif_dbg(efx, hw, efx->net_dev,
 				  "MC command 0x%x inlen %d failed rc=%d\n",
 				  cmd, (int)inlen, -rc);
 	}