[media] media: videobuf2-dma-contig: quiet sparse noise about plain integer as NULL pointer

The function vb2_dma_contig_vaddr returns a void * not an integer.

Quiets the sparse noise:

warning: Using plain integer as NULL pointer
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Pawel Osciak <pawel@osciak.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/videobuf2-dma-contig.c

@@ -85,7 +85,7 @@ static void *vb2_dma_contig_vaddr(void *buf_priv)
 {
 	struct vb2_dc_buf *buf = buf_priv;
 	if (!buf)
-		return 0;
+		return NULL;
 
 	return buf->vaddr;
 }