[WIRELESS] drivers/net/wireless/Kconfig: correct minor typo

Correct minor typo in drivers/net/wireless/Kconfig identified by
Stefano Brivio <stefano.brivio@polimi.it>.

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>