hostap: Add configuration options for NW selection

To cater for different needs add an configuration options for WPA
supplicant network selection (scan results sorting). The default is
still left unchanged.

Signed-off-by: Chaitanya Tata <Chaitanya.Tata@nordicsemi.no>
Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>