leds: gpio: Drop unneeded manual of_node assignment

This reverts the main change of commit bff23714 ("leds: leds-gpio:
Set of_node for created LED devices") because of_node assignment is
handled by core since commit 7ea79ae8 ("leds: gpio: use OF variant
of LED registering function").  Basically the code was overwriting the
of_node with same value.

No functional change expected.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Tested-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>