usb: gadget: uvc: Set the V4L2 buffer field to V4L2_FIELD_NONE

The UVC gadget driver doesn't support interlaced video but left the
buffer field uninitialized. Set it to V4L2_FIELD_NONE.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/uvc_queue.c

@@ -380,6 +380,7 @@ static struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
 	else
 		nextbuf = NULL;
 
+	buf->buf.v4l2_buf.field = V4L2_FIELD_NONE;
 	buf->buf.v4l2_buf.sequence = queue->sequence++;
 	v4l2_get_timestamp(&buf->buf.v4l2_buf.timestamp);