mips/pic32/pic32mzda: Fix refcount leak bugs

of_find_matching_node(), of_find_compatible_node() and
of_find_node_by_path() will return node pointers with refcout
incremented. We should call of_node_put() when they are not
used anymore.

Signed-off-by: Liang He <windhl@126.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>