[MIPS] Change PCI host bridge setup/resources

PCI host bridge setup for SNI RM machines with PCI is quite broken, now
that Linux does it's resource setup own its own. It will use IO addresses,
which are needed by the EISA config detection and assigns PCI memory
addresses, which overlap with ISA legacy addresses (video ram). Below
is a patch, which changes the way how the PCI memory addresses are
used and sets the minimum IO address to give enough IO space for
8 EISA slots). This patch needs the other PCI resource change, I've
posted.

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