dt-bindings: leds: Add LED_FUNCTION_WAN_ONLINE for Internet access

It's common for routers to have LED indicating link on the WAN port.

Some devices however have an extra LED that's meant to be used if WAN
connection is actually "online" (there is Internet access available).

It was suggested to add #define for such use case.

Link: https://lore.kernel.org/linux-devicetree/80e92209-5578-44e7-bd4b-603a29053ddf@collabora.com/T/#u


Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20240223112223.1368-1-zajec5@gmail.com


Signed-off-by: Lee Jones <lee@kernel.org>