drm/exynos: drm_rotator: Fix incorrect usage of IS_ERR_OR_NULL

Use IS_ERR instead of IS_ERR_OR_NULL on clk_get results.
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: NInki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_rotator.c

@@ -674,7 +674,7 @@ static int rotator_probe(struct platform_device *pdev)
 	}
 
 	rot->clock = devm_clk_get(dev, "rotator");
-	if (IS_ERR_OR_NULL(rot->clock)) {
+	if (IS_ERR(rot->clock)) {
 		dev_err(dev, "failed to get clock\n");
 		ret = PTR_ERR(rot->clock);
 		goto err_clk_get;