[media] xc5000: Add support for DMB-TH and ISDB-T

xc5000 is just a tuner, not a decoder, so both DMB-TH and ISDB-T should
work properly there: it is just a matter of teaching the driver what
saw filter should be used and how to calculate the center frequency.

Requested-by: Choi Wing Chan <chanchoiwing@gmail.com>
Cc: Steven Toth <stoth@linuxtv.org>
Cc: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>