[ARM] 3459/1: ixp23xx: fix debug serial macros for big-endian operation

Patch from Lennert Buytenhek

The debug-8250 macros do byte accesses, which means that if we're in
big-endian mode, we need to logically OR the UART address with 3, as
the LSB byte lane (where UART data and status is transferred) has the
highest byte address in the word when we are in big-endian mode.

It's unclear why this problem didn't surface earlier.

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