V4L/DVB (5456): Dvb-pll: Move IF frequency from per-band data to per-tuner data

The IF frequency was specified for each band, but it's not something that
changes from band to band.  None of the tuner definitions had a different
IF frequency (called offset) from one band to another.
Acked-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>