greybus: sdio: fix call to stop command if no data exist

If data is not available the stop command could dereference NULL.
Fetch the stop command directly from the request instead.
Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/sdio.c

@@ -443,8 +443,8 @@ static void gb_sdio_mrq_work(struct work_struct *work)
 			goto done;
 	}
 
-	if (mrq->data->stop) {
-		ret = gb_sdio_command(host, mrq->data->stop);
+	if (mrq->stop) {
+		ret = gb_sdio_command(host, mrq->stop);
 		if (ret < 0)
 			goto done;
 	}