m68knommu: add definitions for the third interrupt controller on devices that don't have a third interrupt controller.

Extending the interrupt controller code in  intc-simr.c to support the third
interrupt controller on the m5441x means we need to add defines (as 0) for the
third interrupt controller on devices that don't have a third interrupt
controller.
Signed-off-by: Steven King <sfking@fdwdc.com>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>