ath9k: uses/needs led_classdev_[un]register

ath9k uses LED classdev functions, so it needs to either select or depend
on them.  This patch uses the same selects that ath5k uses...

drivers/built-in.o: In function `ath_unregister_led':
main.c:(.text+0x138c1d): undefined reference to `led_classdev_unregister'
drivers/built-in.o: In function `ath_register_led':
main.c:(.text+0x139c16): undefined reference to `led_classdev_register'
make[1]: *** [.tmp_vmlinux1] Error 1

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
cc: Jouni Malinen <jmalinen@atheros.com>
Acked-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>