ath6kl: Clear WPS ctrl flag if zero length IE is received from cfg80211

Connect control flag CONNECT_WPS_FLAG has to be cleared
by default even if the driver receives zero length IE
from cfg80211.

Otherwise this flag would be always set after WPS exchange
which would lead wpa_supplicant to fail to connect with
the received WPS credentials. This issue is observed only
in OPEN security.

kvalo: use cfg80211 instead of CFG in the commit log

Signed-off-by: Raja Mani <rmani@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>