[media] af9035: add log writing if unsupported Xtal freq is given

Supports currently only 12 MHz Xtals. It is better to print log
and not to attach frontend in that case.

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