[media] tea575x: split and export functions

Split ioctl interface from enum_freq_bands, g_tuner and s_hw_freq_seek
functions and export them to be used in other drivers like bttv.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>