coccinelle: iterators: Add for_each_child.cocci script

While iterating over child nodes with the for_each functions, if
control is transferred from the middle of the loop, as in the case
of a break or return or goto, there is no decrement in the
reference counter thus ultimately resulting in a memory leak.

Add this script to detect potential memory leaks caused by
the absence of of_node_put() before break, goto, or, return
statements which transfer control outside the loop.

Signed-off-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Signed-off-by: Julia Lawall <julia.lawall@inria.fr>