Patch from Lennert Buytenhek

This patch converts the ixp2000 serial port over to a platform
serial device.
Signed-off-by: NLennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: NDeepak Saxena <dsaxena@plexity.net>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>