leds: aat1290: Add missing of_node_put

The refcount of device_node increases after of_get_next_available_child()
is called. Make sure it is decremented also in case of DT parsing error.

Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>