[media] it913x: tuner power up routines

Copy forgotten power up registers from it913x-fe driver.
Remove two demod registers as those are already written
by af9033 driver.

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