[media] cx231xx: move analog init code to a separate function

That makes easier to understand the code. It would also help
to add support for having boards with just digital support
on some latter patch, as allowed by some PCB configs.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

diff --cc drivers/media/usb/cx231xx/cx231xx-cards.c
Simple merge