genirq: Make irq_domain_alloc_descs() non static

We will need to use this function to implement irq_reserve_ipi() later. So
make it non static and move the prototype to irqdomain.h to allow using it
outside irqdomain.c

Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
Cc: <jason@lakedaemon.net>
Cc: <marc.zyngier@arm.com>
Cc: <jiang.liu@linux.intel.com>
Cc: <ralf@linux-mips.org>
Cc: <linux-mips@linux-mips.org>
Cc: <lisa.parratt@imgtec.com>
Cc: Qais Yousef <qsyousef@gmail.com>
Link: http://lkml.kernel.org/r/1449580830-23652-8-git-send-email-qais.yousef@imgtec.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 130e1c3..c466cc1 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -213,6 +213,8 @@
 extern struct irq_domain *irq_find_matching_fwnode(struct fwnode_handle *fwnode,
 						   enum irq_domain_bus_token bus_token);
 extern void irq_set_default_host(struct irq_domain *host);
+extern int irq_domain_alloc_descs(int virq, unsigned int nr_irqs,
+				  irq_hw_number_t hwirq, int node);
 
 static inline struct fwnode_handle *of_node_to_fwnode(struct device_node *node)
 {