[MIPS] IP32: Fix unexpected irq 71

It's possible that the crime interrupt handler is called without
pending interrupts (probably a hardware issue). To avoid irritating
"unexpected irq 71" messages, we now just ignore the spurious crime
interrupts.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>