leds: 88pm860x: Add missing of_node_put()

of_find_node_by_name() returns a node pointer with refcount incremented, use
of_node_put() on it when done.

of_find_node_by_name() will call of_node_put() against from parameter,
thus we also need to call of_node_get(from) before calling
of_find_node_by_name().

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>