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/[e-mail]/T/#u
Signed-off-by: Rafał Miłecki <[e-mail]>
Reviewed-by: AngeloGioacchino Del Regno <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

include/dt-bindings/leds/common.h

···
 #define LED_FUNCTION_TX "tx"
 #define LED_FUNCTION_USB "usb"
 #define LED_FUNCTION_WAN "wan"
+#define LED_FUNCTION_WAN_ONLINE "wan-online"
 #define LED_FUNCTION_WLAN "wlan"
 #define LED_FUNCTION_WLAN_2GHZ "wlan-2ghz"
 #define LED_FUNCTION_WLAN_5GHZ "wlan-5ghz"