ARM: prima2: move to use REGMAP APIs for rtciobrg

all devices behind rtciobrg needs a special way to access. currently they
are using a platform-specific API.
this patch moves to REGMAP, then clients can use regmap APIs to read/write.
for the moment, old APIs are still kept, once all clients move to regmap,
old APIs will be dropped.

this patch also does minor clean for comments, authors statement.

Signed-off-by: Guo Zeng <Guo.Zeng@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>