mips: lantiq: falcon: Fix refcount leak bug in sysctrl

In ltq_soc_init(), of_find_compatible_node() will return a node pointer
with refcount incremented. We should use of_node_put() when it is not
used anymore.

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