cx18: Fix S-Video and Compsite input settings for the Yuan MPC718 per user
reports from Yuri Warczynski <Yuri.Warczynski@gmail.com> and
Brian Hope <brian@hopefamily.info> and enable the card entry.  The tuner reset
GPIO pin is likely incorrect as the tuner firmware cannot be reloaded without a
reboot.  It is likely the audio routing is done via GPIO which is not
implemented yet, as users report audio doesn't work for some inputs.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>