[media] em28xx: enable DMABUF

Now that it uses videobuf2, em28xx can support DMABUF.

Tested with an HVR-950 on analog mode and a 2gen i5core machine
with an i915 graphics adapter.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/usb/em28xx/em28xx-video.c

@@ -699,7 +699,7 @@ int em28xx_vb2_setup(struct em28xx *dev)
 	/* Setup Videobuf2 for Video capture */
 	q = &dev->vb_vidq;
 	q->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-	q->io_modes = VB2_READ | VB2_MMAP | VB2_USERPTR;
+	q->io_modes = VB2_READ | VB2_MMAP | VB2_USERPTR | VB2_DMABUF;
 	q->drv_priv = dev;
 	q->buf_struct_size = sizeof(struct em28xx_buffer);
 	q->ops = &em28xx_video_qops;