[MIPS] BCM1480: Fix PCI/HT IO access

- removed check for enable HT-PCI bridges, because some CFE version
  init only the needed one and scanning works even with disabled HT
  links
- implemented I/O access behind HT PCI busses
- fixed pci_map for IO resource behind PCI bridge

Tested with E100 and Tulip driver.

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