V4L/DVB (5609): M920x: group like functions together

- Group the tuner configurations together.
- Group the demod configurations together.
- Group the device-specific initialization functions together.
- Group demod_attach functions together.
- Group tuner_attach functions together.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>