leds: 88pm860x: Fix missing refcount decrement for parent of_node

The driver obtained the reference to parent->of_node but immediately it
was overwritten by reference to child node 'leds'. The of_node_put at
the end of DT parsing function decremented only the child 'leds' so
effectively the reference to parent of_node leaked.

Getting reference to parent->of_node is not needed at all so get rid of
it to fix the reference count.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>