[MIPS] IP27: misc fixes

- fix PCI interrupt assignment by emulating ioc3 interrupt pin register
- use pci_probe_only mode
- select correct page size in bridge
- remove no longer needed ioc3_sio_init() code

[Ralf: Fix for 64kB or larger pagesizes]

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>