[ARM] 3831/1: iop3xx: factor out common register defines

Factor out the register defines for a number of other peripherals
common to the iop32x and iop33x.

Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>