udmabuf: actually unmap the scatterlist

unmap_udmabuf fails to actually unmap the scatterlist, leaving dangling
mappings around.

Fixes: fbb0de79 ("Add udmabuf misc device")
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Link: http://patchwork.freedesktop.org/patch/msgid/20190604202331.17482-1-l.stach@pengutronix.deSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/dma-buf/udmabuf.c

@@ -77,6 +77,7 @@ static void unmap_udmabuf(struct dma_buf_attachment *at,
 			  struct sg_table *sg,
 			  enum dma_data_direction direction)
 {
+	dma_unmap_sg(at->dev, sg->sgl, sg->nents, direction);
 	sg_free_table(sg);
 	kfree(sg);
 }