staging: axis-fifo: fix return value check in axis_fifo_probe()

In case of error, the function device_create() returns ERR_PTR() and
never returns NULL. The NULL test in the return value check should be
replaced with IS_ERR().

Fixes: 4a965c5f89de ("staging: add driver for Xilinx AXI-Stream FIFO v4.1 IP core")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/axis-fifo/axis-fifo.c

@@ -1006,10 +1006,10 @@ static int axis_fifo_probe(struct platform_device *pdev)
 	/* create driver file */
 	fifo->device = device_create(axis_fifo_driver_class, NULL, fifo->devt,
 				     NULL, device_name);
-	if (!fifo->device) {
+	if (IS_ERR(fifo->device)) {
 		dev_err(fifo->dt_device,
 			"couldn't create driver file\n");
-		rc = -ENOMEM;
+		rc = PTR_ERR(fifo->device);
 		goto err_chrdev_region;
 	}
 	dev_set_drvdata(fifo->device, fifo);