[POWERPC] Add IRQ remapping hook

This patch adds irq remapping hook. On interrupt mechanism on Beat,
when an irq outlet which has an id which is formerly used is created,
remapping the irq is required.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/irq.c

@@ -604,6 +604,8 @@ unsigned int irq_create_mapping(struct irq_host *host,
 	 */
 	virq = irq_find_mapping(host, hwirq);
 	if (virq != IRQ_NONE) {
+		if (host->ops->remap)
+			host->ops->remap(host, virq, hwirq);
 		pr_debug("irq: -> existing mapping on virq %d\n", virq);
 		return virq;
 	}

include/asm-powerpc/irq.h

@@ -89,6 +89,9 @@ struct irq_host_ops {
 	/* Dispose of such a mapping */
 	void (*unmap)(struct irq_host *h, unsigned int virq);
 
+	/* Update of such a mapping  */
+	void (*remap)(struct irq_host *h, unsigned int virq, irq_hw_number_t hw);
+
 	/* Translate device-tree interrupt specifier from raw format coming
 	 * from the firmware to a irq_hw_number_t (interrupt line number) and
 	 * type (sense) that can be passed to set_irq_type(). In the absence