[MIPS] Register PCI host bridge resource earlier

PCI based SNI RM machines have their EISA bus behind an Intel PCI/EISA
bridge. So the PCI IO range must start at 0x0000. Changing that will
break the PCI bus, because i8259.c already has registered it's IO
addresses before the PCI bus gets initialized. Below is a patch,
which will register the PCI host bridge resources inside
register_pci_controller(). It also changes i8259.c to use insert_region(),
because request_resource() will fail, if the IO space of the PIT hanging
of the PCI host bridge (maybe passing the resource parent to
init_i8259_irqs() is a cleaner fix for that).

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