[media] em28xx: Fix vidioc fmt vid cap v4l2 compliance

Set fmt.pix.priv to zero in vidioc_try_fmt_vid_cap.
Catched by v4l2-compliance.

Signed-off-by: Alban Browaeys <prahal@yahoo.com>
[hans.verkuil@cisco.com: dropping unnecessary change to g_fmt_vid_cap]
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

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

@@ -1008,6 +1008,7 @@ static int vidioc_try_fmt_vid_cap(struct file *file, void *priv,
 	else
 		f->fmt.pix.field = dev->interlaced ?
 			   V4L2_FIELD_INTERLACED : V4L2_FIELD_TOP;
+	f->fmt.pix.priv = 0;
 
 	return 0;
 }