[media] rtl2832: merge reg page as a part of reg address

Chips uses 8-bit register addresses with 5 pages. Extend register
address by using register page as a first byte of address, defining
virtual register addresses. That is common method of handling
register pages and regmap also uses it. Remove page + address
conversion glue which was there for regmap.

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