ARM: cns3xxx: Use IO memory accessors everywhere

Before it isn't too late let's switch to IO memory accessors.
This patch converts all current _REG users and _REG definitions.
There should be no functional changes.

Suggested-by: Ben Dooks <ben-linux@fluff.org>
Suggested-by: Sergei Shtylyov <sshtylyov@mvista.com>
Signed-off-by: Anton Vorontsov <avorontsov@mvista.com>