genirq: Make create/destroy_irq() ia64 private

No more users outside of itanic. Confine it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Grant Likely <grant.likely@linaro.org>
Tested-by: Tony Luck <tony.luck@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/20140507154338.700598389@linutronix.de


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