[media] it913x: change reg read/write routines more common

Change register write and read routines to similar which are
typically used. We have to add processor core as a part of register
address in order to simplify register access. Chip has two cores,
called link and ofdm. As for now, use address bit 24 to address used
core. Bits 15:0 are register address in given core.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>