package/wpa_supplicant: adding ifupdown support

package/wpa_supplicant: adding ifupdown support

Actually, configuring a wifi interface as per "interfaces" man:

auto wlan0
iface wlan0 inet dhcp
wpa-conf /etc/wpa_supplicant.conf

doesn't work on buildroot because the line wpa-conf is ignored due to
the lack of a proper ifupdown script to handle the wpa_supplicant
initialization.

Signed-off-by: Angelo Compagnucci <[email protected]>
Reviewed-by: Nicolas Cavallari <[email protected]>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <[email protected]>