V4L (0988): Tuner cleanups by removing Video IF from tuners struct

- Video IF was removed from tuners struct.
- Each Video standard have its own Video IF frequency, so it
is related to video standard. Of course tuner also needs
saw filters for IF, but this way, similar tuners can be grouped
into just one entry, if they have the same cut-off freqs and
the same switch config and global config.
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>