powerpc/83xx: Fix incorrect PCI interrupt map in SBC834x DTS

Allows interrupts to occur on the sbc834x. Currently PCI devices
get assigned an incorrect IRQ and so the interrupt count never
increases. This was tested with the 82546GB based dual port E1000
PCI-X NIC which uses two distinct IRQ lines on the one card.

root@localhost:/root> cat /proc/interrupts | grep eth
17:         78   IPIC   Level     eth1
48:      27121   IPIC   Level     eth0

Signed-off-by: Liang Li <liang.li@windriver.com>
Signed-off-by: Yang Shi <yang.shi@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>