wpa_supplicant: use select instead of epoll

As discussed with Gustavo on the mailing-list, remove EPOLL flag.
wpa_supplicant isn't able to answer DBUS message as events are
never delivered.

Signed-off-by: Eric Limpens <limpens@gmail.com>
Acked-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>