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>

arch/tile/include/asm/irq.h

@@ -76,4 +76,7 @@ void tile_irq_activate(unsigned int irq, int tile_irq_type);
 
 void setup_irq_regs(void);
 
+unsigned int irq_alloc_hwirq(int node);
+void irq_free_hwirq(unsigned int irq);
+
 #endif /* _ASM_TILE_IRQ_H */

arch/tile/kernel/irq.c

@@ -312,4 +312,16 @@ void destroy_irq(unsigned int irq)
 	spin_unlock_irqrestore(&available_irqs_lock, flags);
 }
 EXPORT_SYMBOL(destroy_irq);
+
+unsigned int irq_alloc_hwirq(int node)
+{
+	int ret = create_irq();
+	return ret < 0 ? 0 : ret;
+}
+
+void irq_free_hwirq(unsigned int irq)
+{
+	destroy_irq(irq);
+}
+
 #endif