wireless: airo_cs needs WEXT_SPY

airo_cs uses spy interfaces so it needs to select WEXT_SPY.

ERROR: "iw_handler_set_thrspy" [drivers/net/wireless/airo.ko] undefined!
ERROR: "wireless_spy_update" [drivers/net/wireless/airo.ko] undefined!
ERROR: "iw_handler_get_spy" [drivers/net/wireless/airo.ko] undefined!
ERROR: "iw_handler_get_thrspy" [drivers/net/wireless/airo.ko] undefined!
ERROR: "iw_handler_set_spy" [drivers/net/wireless/airo.ko] undefined!

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>