drm/exynos: dsi: use IS_ERR() to check devm_ioremap_resource() results

devm_ioremap_resource() returns an error pointer, not NULL. Thus,
the result should be checked with IS_ERR().
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/exynos/exynos_drm_dsi.c

@@ -1426,9 +1426,9 @@ static int exynos_dsi_probe(struct platform_device *pdev)
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	dsi->reg_base = devm_ioremap_resource(&pdev->dev, res);
-	if (!dsi->reg_base) {
+	if (IS_ERR(dsi->reg_base)) {
 		dev_err(&pdev->dev, "failed to remap io region\n");
-		return -EADDRNOTAVAIL;
+		return PTR_ERR(dsi->reg_base);
 	}
 
 	dsi->phy = devm_phy_get(&pdev->dev, "dsim");