[POWERPC] 85xx: sbc8548 - Fix incorrect PCI-X and PCI interrupt map

The following patch allows interrupts to occur on the
sbc8548. Currently PCI and PCI-X devices get assigned an IRQ
but the interrupt count never increases.  This solves the
problem and adds PCI support as well.

Signed-off-by: Jeremy McNicoll <jeremy.mcnicoll@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>