powerpc/cell: add missing of_node_put

for_each_node_by_name 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,e1;
local idexpression n;
@@

 for_each_node_by_name(n, e1) {
   ... when != of_node_put(n)
       when != e = n
(
   return n;
|
+  of_node_put(n);
?  return ...;
)
   ...
 }
// </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/1448051604-25256-7-git-send-email-Julia.Lawall@lip6.fr

arch/powerpc/platforms/cell/iommu.c

@@ -977,6 +977,7 @@ static int __init cell_iommu_fixed_mapping_init(void)
 			if (hbase < dbase || (hend > (dbase + dsize))) {
 				pr_debug("iommu: hash window doesn't fit in"
 					 "real DMA window\n");
+				of_node_put(np);
 				return -1;
 			}
 		}