drm/shmob: Fix return value check in shmob_drm_probe

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

Fixes: 8f1597c8 ("drm: shmobile: Perform initialization/cleanup at probe/remove time")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/shmobile/shmob_drm_drv.c

@@ -229,8 +229,8 @@ static int shmob_drm_probe(struct platform_device *pdev)
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	sdev->mmio = devm_ioremap_resource(&pdev->dev, res);
-	if (sdev->mmio == NULL)
-		return -ENOMEM;
+	if (IS_ERR(sdev->mmio))
+		return PTR_ERR(sdev->mmio);
 
 	ret = shmob_drm_setup_clocks(sdev, pdata->clk_source);
 	if (ret < 0)