Switch to using irq_handler_t for interrupt function handler pointers.

Change name of m68knommu's irq_hanlder_t data structure so it doesn't
clash with the common type (include/linux/interrupt.h).
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>