tile: Implement irq_alloc/free_hwirq() for migration

We want to convert the drivers over to the new interface and finally
tile to sparse irqs. Implement irq_alloc/free_hwirq() for step by step
migration.

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>
Acked-by: Chris Metcalf <cmetcalf@tilera.com>
Link: http://lkml.kernel.org/r/20140507154336.947853241@linutronix.de


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