mwifiex: fix incorrect privacy setting in beacon and probe response

Test procedure:
1. Start AP with security setting (e.g. WPA2)
2. Stop AP
3. Start AP with open security

Here it's observed that privacy is enabled in beacons and
probe responses.

This patch fixes it by checking the privacy parameter from
cfg80211_ap_settings. If privacy is not set in cfg80211_ap_settings,
set open authentication and no encryption in FW.

Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>