drm/exynos: fix wrong return check for platform_device_register_simple

platform_device_register_simple() never returns NULL, but IS_ERR_OR_NULL macro
is used for checking return value in exynos drm driver.
Signed-off-by: NSeung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_drv.c

@@ -388,7 +388,7 @@ static int __init exynos_drm_init(void)
 
 	exynos_drm_pdev = platform_device_register_simple("exynos-drm", -1,
 				NULL, 0);
-	if (IS_ERR_OR_NULL(exynos_drm_pdev)) {
+	if (IS_ERR(exynos_drm_pdev)) {
 		ret = PTR_ERR(exynos_drm_pdev);
 		goto out;
 	}

drivers/gpu/drm/exynos/exynos_drm_hdmi.c

@@ -56,7 +56,7 @@ int exynos_platform_device_hdmi_register(void)
 
 	exynos_drm_hdmi_pdev = platform_device_register_simple(
 			"exynos-drm-hdmi", -1, NULL, 0);
-	if (IS_ERR_OR_NULL(exynos_drm_hdmi_pdev))
+	if (IS_ERR(exynos_drm_hdmi_pdev))
 		return PTR_ERR(exynos_drm_hdmi_pdev);
 
 	return 0;