[media] vb2: don't free alloc context if it is ERR_PTR

Don't try to free a pointer containing an ERR_PTR().

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Pawel Osciak <pawel@osciak.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/v4l2-core/videobuf2-dma-contig.c

@@ -854,7 +854,8 @@ EXPORT_SYMBOL_GPL(vb2_dma_contig_init_ctx);
 
 void vb2_dma_contig_cleanup_ctx(void *alloc_ctx)
 {
-	kfree(alloc_ctx);
+	if (!IS_ERR_OR_NULL(alloc_ctx))
+		kfree(alloc_ctx);
 }
 EXPORT_SYMBOL_GPL(vb2_dma_contig_cleanup_ctx);