leds: Use fwnode_for_each_child_node() instead

leds: Use fwnode_for_each_child_node() instead

fwnode_for_each_child_node() is now the same as
fwnode_for_each_available_child_node() on all backends (OF, ACPI and
swnode). In order to remove the available variants, switch the uses to
non-available variants.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Lee Jones <lee@kernel.org>