m68knommu: move some init code out of unmask routine for ColdFire intc-2

Use a proper irq_startup() routine to intialize the interrupt priority
and level register in the ColdFire intc-2 controller code. We shouldn't
be checking if the priority/level has been set on every unmask operation.

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