V4L/DVB (12490): Report only 32kHz for ALSA

There are several reasons:

 - SAA7133/35 uses DDEP (DemDec Easy Programming mode), which works in 32kHz
   only
 - SAA7134 for TV mode uses DemDec mode (32kHz)
 - Radio works in 32kHz only
 - When recording 48kHz from Line1/Line2, switching of capture source to TV
   means switching to 32kHz without any frequency translation

Signed-off-by: Oldřich Jedlička <oldium.pro@seznam.cz>
Acked-by: hermann pitton <hermann-pitton@arcor.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>