ARM: orion5x: use fixed PCI i/o mapping

Move orion5x PCI to fixed i/o mapping and remove io.h.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>