leds: max77693: Add missing of_node_put

Each break out of the for_each_available_child_of_node loop requires
of_node_put().

This patch adds missing of_node_put() when loop breaks on conflicting
values of led-sources DT property.

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