m68knommu: add prototype for ack_bad_irq

Create prototype for ack_bad_irq() for m68knommu.
Compilation of kernel/irq/handle.c fails without it.
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-m68knommu/hardirq.h

@@ -22,4 +22,6 @@ typedef struct {
 # error HARDIRQ_BITS is too low!
 #endif
 
+void ack_bad_irq(unsigned int irq);
+
 #endif /* __M68K_HARDIRQ_H */