drm/mediatek: check for memory allocation failure

If 'devm_kmalloc_array' returns NULL, we should return -ENOMEM as already
done a few lines above instead of deferencing a NULL pointer a few lines
below.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: CK Hu <ck.hu@mediatek.com>

drivers/gpu/drm/mediatek/mtk_drm_crtc.c

@@ -559,6 +559,8 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
 	mtk_crtc->ddp_comp = devm_kmalloc_array(dev, mtk_crtc->ddp_comp_nr,
 						sizeof(*mtk_crtc->ddp_comp),
 						GFP_KERNEL);
+	if (!mtk_crtc->ddp_comp)
+		return -ENOMEM;
 
 	mtk_crtc->mutex = mtk_disp_mutex_get(priv->mutex_dev, pipe);
 	if (IS_ERR(mtk_crtc->mutex)) {