sparc64: Fix irq_of_parse_and_map() and irq_dispose_mapping().

Stephen Rothwell noticed that I committed an earlier version
of the patch that didn't have two things fixed:

1) irq_of_parse_and_map() should return "unsigned int" not "int"
   and it should return zero for "no irq"

2) irq_dispose_mapping() should be an inline function, not a macro,
   for type checking

With feedback and suggestions from Anton Vorontsov.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc/include/asm/prom.h b/arch/sparc/include/asm/prom.h
index 58b85fa..900d447 100644
--- a/arch/sparc/include/asm/prom.h
+++ b/arch/sparc/include/asm/prom.h
@@ -101,8 +101,10 @@
  * register them in the of_device objects, whereas powerpc computes them
  * on request.
  */
-extern int irq_of_parse_and_map(struct device_node *node, int index);
-#define irq_dispose_mapping(irq) do { } while (0)
+extern unsigned int irq_of_parse_and_map(struct device_node *node, int index);
+static inline void irq_dispose_mapping(unsigned int virq)
+{
+}
 
 /*
  * NB:  This is here while we transition from using asm/prom.h