drm/tegra: Fix return value check

In case of error, the devm_ioremap_resource() function returns ERR_PTR()
and never NULL. The NULL test in the return value check should therefore
be replaced with IS_ERR().
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NThierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dsi.c

@@ -886,8 +886,8 @@ static int tegra_dsi_probe(struct platform_device *pdev)
 
 	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	dsi->regs = devm_ioremap_resource(&pdev->dev, regs);
-	if (!dsi->regs)
-		return -EADDRNOTAVAIL;
+	if (IS_ERR(dsi->regs))
+		return PTR_ERR(dsi->regs);
 
 	tegra_dsi_initialize(dsi);