Barebox of_find_node_by_path requires a node to be passed as start node
to start searching. Linux OF API does not pass this node and no current
user of it in barebox is passing anything else than the root node.
Therefore, we rename current function to of_find_node_by_path_from and
introduce a Linux OF API compatible of_find_node_by_path that always
passes the current root_node. Also, all current users of that function
are updated to reflect the API change.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>