of_find_node_by_name suffers from infinite looping, because it
does not check for root node of the tree iterated over. This
fixes this by checking for node->parent to determine whether
the last node has been reached.
Since of_tree_for_each_node does not iterate over the whole tree,
but only over the remaining nodes, rename it to
of_tree_for_each_node_from.

Reported-by: NISHIMOTO Hiroki <hiroki.nishimoto.if@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>