buildroot

wpa_supplicant: explicitly disable libnl by default

libnl support is enabled by default since version 1.0, so disable it
to avoid build breakage when there's no libnl.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>