powerpc/chrp/nvram.c: Add of_node_put to avoid memory leak

Add a call to of_node_put in the error handling code following a call to
of_find_node_by_type.

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

// <smpl>
@r exists@
local idexpression x;
expression E,E1,E2;
statement S;
@@

*x =
(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
)(...);
...
if (x == NULL) S
<... when != x = E
*if (...) {
  ... when != of_node_put(x)
      when != if (...) { ... of_node_put(x); ... }
(
  return <+...x...+>;
|
*  return ...;
)
}
...>
(
E2 = x;
|
of_node_put(x);
)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/chrp/nvram.c

@@ -74,8 +74,10 @@ void __init chrp_nvram_init(void)
 		return;
 
 	nbytes_p = of_get_property(nvram, "#bytes", &proplen);
-	if (nbytes_p == NULL || proplen != sizeof(unsigned int))
+	if (nbytes_p == NULL || proplen != sizeof(unsigned int)) {
+		of_node_put(nvram);
 		return;
+	}
 
 	nvram_size = *nbytes_p;