drm/sun4i: Make sun4i_crtc_init return ERR_PTR style error codes

sun4i_crtc_init can fail for a number of reasons. Instead of returning
a NULL pointer when it fails, pass back the encountered error using
ERR_PTR.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

drivers/gpu/drm/sun4i/sun4i_crtc.c

@@ -145,7 +145,7 @@ struct sun4i_crtc *sun4i_crtc_init(struct drm_device *drm)
 
 	scrtc = devm_kzalloc(drm->dev, sizeof(*scrtc), GFP_KERNEL);
 	if (!scrtc)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	scrtc->drv = drv;
 
 	ret = drm_crtc_init_with_planes(drm, &scrtc->crtc,
@@ -155,7 +155,7 @@ struct sun4i_crtc *sun4i_crtc_init(struct drm_device *drm)
 					NULL);
 	if (ret) {
 		dev_err(drm->dev, "Couldn't init DRM CRTC\n");
-		return NULL;
+		return ERR_PTR(ret);
 	}
 
 	drm_crtc_helper_add(&scrtc->crtc, &sun4i_crtc_helper_funcs);

drivers/gpu/drm/sun4i/sun4i_drv.c

@@ -125,9 +125,9 @@ static int sun4i_drv_bind(struct device *dev)
 
 	/* Create our CRTC */
 	drv->crtc = sun4i_crtc_init(drm);
-	if (!drv->crtc) {
+	if (IS_ERR(drv->crtc)) {
 		dev_err(drm->dev, "Couldn't create the CRTC\n");
-		ret = -EINVAL;
+		ret = PTR_ERR(drv->crtc);
 		goto cleanup_mode_config;
 	}
 	drm->irq_enabled = true;