TP-Link TL-WR902AC has another one, tiny LED inside RJ45 socket which is
attached to GPIO15. Add support for it, use it as a "lan" LED and rename
old one to "internet". Also, fix uci option name for "lan" LED in system
configuration ("wan" -> "lan").
Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>