Coccinelle: Add iterators/fen.cocci

for_each_node iterators only exit normally when the loop cursor is
NULL, so there is no point to call of_node_put on the final value.

Signed-off-by: Nicolas Palix <npalix@diku.dk>
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Michal Marek <mmarek@suse.cz>