Staging: ath6kl: ATH6KL_CFG80211 depends on CFG80211

ATH6KL_CFG80211 should depend on CFG80211 to fix build errors:

ERROR: "wiphy_free" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "cfg80211_inform_bss_frame" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "__ieee80211_get_channel" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "cfg80211_get_bss" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "wiphy_unregister" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "cfg80211_connect_result" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "cfg80211_michael_mic_failure" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "cfg80211_ibss_joined" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "cfg80211_roamed" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "cfg80211_put_bss" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "wiphy_new" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "wiphy_register" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "cfg80211_disconnected" [drivers/staging/ath6kl/ath6kl.ko] undefined!
ERROR: "cfg80211_scan_done" [drivers/staging/ath6kl/ath6kl.ko] undefined!

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Vipin Mehta <vmehta@atheros.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>