Input: cobalt_btns - add missing MODULE_LICENSE

Export the module license and other information about the Cobalt
button module in order to avoid the following warning:

| WARNING: modpost: missing MODULE_LICENSE() in drivers/input/misc/cobalt_btns.o

Signed-off-by: Martin Michlmayr <tbm@cyrius.com>
Acked-by: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>