irq_domain: Centralize definition of irq_dispose_mapping()

Several architectures define their own empty irq_dispose_mapping().  Since
the irq_domain code is centralized now, there is little need to do so.  This
patch removes them and creates a new empty copy when !CONFIG_IRQ_DOMAIN is
selected.

The patch also means that IRQ_DOMAIN becomes selectable on all architectures.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: sparclinux@vger.kernel.org
Cc: linux@lists.openrisc.net

include/linux/of_irq.h

@@ -6,6 +6,7 @@ struct of_irq;
 #include <linux/types.h>
 #include <linux/errno.h>
 #include <linux/irq.h>
+#include <linux/irqdomain.h>
 #include <linux/ioport.h>
 #include <linux/of.h>
 
@@ -65,9 +66,6 @@ extern int of_irq_map_one(struct device_node *device, int index,
 extern unsigned int irq_create_of_mapping(struct device_node *controller,
 					  const u32 *intspec,
 					  unsigned int intsize);
-#ifdef CONFIG_IRQ_DOMAIN
-extern void irq_dispose_mapping(unsigned int irq);
-#endif
 extern int of_irq_to_resource(struct device_node *dev, int index,
 			      struct resource *r);
 extern int of_irq_count(struct device_node *dev);