V4L/DVB (7277): bttv: Re-enabling radio support requires the use of struct bttv_fh

A number of the radio tuner ioctl functions are shared with the TV
tuner, these functions require a struct bttv_fh data structure to be
allocated and initialized.

Signed-off-by: Robert Fitzsimons <robfitz@273k.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>