drm/imx/lcdc: fix a NULL vs IS_ERR() bug in probe

The devm_drm_dev_alloc() function returns error pointers.  It never
returns NULL.  Fix the check.

Fixes: c87e859c ("drm/imx/lcdc: Implement DRM driver for imx25")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/d0a1fc55-3ef6-444e-b3ef-fdc937d8d57a@kili.mountain

drivers/gpu/drm/imx/lcdc/imx-lcdc.c

@@ -400,8 +400,8 @@ static int imx_lcdc_probe(struct platform_device *pdev)
 
 	lcdc = devm_drm_dev_alloc(dev, &imx_lcdc_drm_driver,
 				  struct imx_lcdc, drm);
-	if (!lcdc)
-		return -ENOMEM;
+	if (IS_ERR(lcdc))
+		return PTR_ERR(lcdc);
 
 	drm = &lcdc->drm;