m68knommu: general interrupt controller for ColdFire many 52xx parts

Create general interrupt controller code for the many ColdFire version 2
cores that use the two region INTC interrupt controller. This includes the
523x family, 5270, 5271, 5274, 5275, and the 528x families.

This code does proper masking and unmasking of interrupts. With this in
place some of the driver hacks in place to support ColdFire interrupts
can finally go away.

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