V4L/DVB: af9013: program tuner before demodulator

Program tuner before demodulator in case of channel set. Earlier it was
programmed during demodulator programming. This seems to resolve weird
error where demodulator misses sometimes ability to gain lock.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>