[PATCH] m68knommu: implement irq_canonicalize()

Add a null definition for irq_canonicalize(). It is used in the gerneric
serial subsystem code, can't compile without it.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>