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/kernel/of_device.c b/arch/sparc/kernel/of_device.c
index 56e9a71..aace71f 100644
--- a/arch/sparc/kernel/of_device.c
+++ b/arch/sparc/kernel/of_device.c
@@ -29,12 +29,12 @@
 }
 EXPORT_SYMBOL(of_find_device_by_node);
 
-int irq_of_parse_and_map(struct device_node *node, int index)
+unsigned int irq_of_parse_and_map(struct device_node *node, int index)
 {
 	struct of_device *op = of_find_device_by_node(node);
 
 	if (!op || index >= op->num_irqs)
-		return 0xffffffff;
+		return 0;
 
 	return op->irqs[index];
 }