[media] videobuf_pages_to_sg: sglist[0] length problem

On function videobuf_pages_to_sg the statement sg_set_page(&sglist[0],
pages[0], PAGE_SIZE - offset, offset) will fail if size is less than
PAGE_SIZE.
Signed-off-by: NNewson Edouard <newsondev@gmail.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/videobuf-dma-sg.c

@@ -108,8 +108,9 @@ static struct scatterlist *videobuf_pages_to_sg(struct page **pages,
 	if (PageHighMem(pages[0]))
 		/* DMA to highmem pages might not work */
 		goto highmem;
-	sg_set_page(&sglist[0], pages[0], PAGE_SIZE - offset, offset);
-	size -= PAGE_SIZE - offset;
+	sg_set_page(&sglist[0], pages[0],
+			min_t(size_t, PAGE_SIZE - offset, size), offset);
+	size -= min_t(size_t, PAGE_SIZE - offset, size);
 	for (i = 1; i < nr_pages; i++) {
 		if (NULL == pages[i])
 			goto nopage;