commit 2502b667 ("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: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NGreg Ungerer <gerg@uclinux.org>