[media] xc4000: get rid of hard-coded 8MHz firmware config

Remove a hack I had put in to force the firmware to be 8MHz, now setting
the firmware properly based on the target standard.

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>