mips: Kill pointless destroy_irq()

Copy and paste leftovers with no functionality at all.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Grant Likely <grant.likely@linaro.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Jayachandran C <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Link: http://lkml.kernel.org/r/20140507154334.008113902@linutronix.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>