powerpc/6xx: add missing of_node_put

for_each_compatible_node performs an of_node_get on each iteration, so
a break out of the loop requires an of_node_put.

A simplified version of the semantic patch that fixes this problem is as
follows (http://coccinelle.lip6.fr):

// <smpl>
@@
expression e;
local idexpression n;
@@

@@
local idexpression n;
expression e;
@@

 for_each_compatible_node(n,...) {
   ...
(
   of_node_put(n);
|
   e = n
|
+  of_node_put(n);
?  break;
)
   ...
 }
... when != n
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1448051604-25256-2-git-send-email-Julia.Lawall@lip6.fr

arch/powerpc/platforms/embedded6xx/hlwd-pic.c

@@ -214,6 +214,7 @@ void hlwd_pic_probe(void)
 			irq_set_chained_handler(cascade_virq,
 						hlwd_pic_irq_cascade);
 			hlwd_irq_host = host;
+			of_node_put(np);
 			break;
 		}
 	}