[media] tvp5150: allow get/set_fmt on the video source pad

To let userspace propagate formats downstream in a media controller
scenario, the video source pad (now pad 1, DEMOD_PAD_VID_OUT) must allow
setting and getting the format. Incidentally, tvp5150_fill_fmt was
implemented for this pad, not for the new analog input pad (now pad 0,
DEMOD_PAD_IF_INPUT).

Fixes: 55606310 ("[media] tvp5150: create the expected number of pads")

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>