m68knommu: add support for second interrupt controller of ColdFire 5249

The ColdFire 5249 CPU has a second (compleletly different) interrupt
controller. It is the only ColdFire CPU that has this type. It controlls
GPIO interrupts amongst a number of interrupts from other internal
peripherals. Add support code for it.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>