hostap: Fix the security mode in AP

For AP we should use the security mode from the SSID as stations can
have a different security than the configure one. E.g., WPA/WPA2 in AP
vs WPA in STA1 and WPA2 in STA2.

Signed-off-by: Chaitanya Tata <Chaitanya.Tata@nordicsemi.no>