m68k: Revive reporting of spurious interrupts

commit 2502b667ea ("Change the m68knommu irq
handling to use the generic irq framework.") removed the reporting of spurious
interrupts on nommu (68328 and 68360).

Bring it back in a generic way, using "atomic_t irq_err_count", as that's what
most of the other architectures are using.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>

arch/m68k/platform/68360/ints.c

@@ -34,9 +34,6 @@ asmlinkage void inthandler(void);
 
 extern void *_ramvec[];
 
-/* The number of spurious interrupts */
-volatile unsigned int num_spurious;
-
 static void intc_irq_unmask(struct irq_data *d)
 {
 	pquicc->intr_cimr |= (1 << d->irq);