powerpc/irq.c: Add of_node_put to avoid memory leak

Author: Julia Lawall <julia@diku.dk>

In this case, a device_node structure is stored in another structure that
is then freed without first decrementing the reference count of the
device_node structure.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// 
@r exists@
expression x;
identifier f;
position p1,p2;
@@

x@p1->f = \(of_find_node_by_path\|of_find_node_by_name\|of_find_node_by_phandle\|of_get_parent\|of_get_next_parent\|of_get_next_child\|of_find_compatible_node\|of_match_node\|of_find_node_by_type\|of_find_node_with_property\|of_find_matching_node\|of_parse_phandle\|of_node_get\)(...);
... when != of_node_put(x)
kfree@p2(x)

@script:python@
p1 << r.p1;
p2 << r.p2;
@@
cocci.print_main("call",p1)
cocci.print_secs("free",p2)
// 

Signed-off-by: Julia Lawall 
Signed-off-by: Benjamin Herrenschmidt 

---
 arch/powerpc/kernel/irq.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
 
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 47fbc56..4002b48 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -587,8 +587,10 @@ struct irq_host *irq_alloc_host(struct device_node *of_node,
 			 * this will be fixed once slab is made available early
 			 * instead of the current cruft
 			 */
-			if (mem_init_done)
+			if (mem_init_done) {
+				of_node_put(host->of_node);
 				kfree(host);
+			}
 			return NULL;
 		}
 		irq_map[0].host = host;