wifi-scripts: ucode: fix bug moving to empty wifi-station config

wifi-scripts: ucode: fix bug moving to empty wifi-station config

When transitioning from a config with one or more wifi-stations, to a configuration
that has no wifi-station; the file would not be empty/reset and the old wifi-station
entries would remain.

This is because iface_wpa_stations and iface_sae_stations return early if there
are no wifi-stations present, which is an incorrect behavior as it causes the
file to actually have old entries.

'sae_password_file' and 'wpa_psk_file' are also set by default inside
of iface_auth_type to same path as the one used by wifi-station, so it
is indeed going to be set in the config and would contain the old
entries.

This happens with reload and wifi restart. So the only solution
would be to manually remove the file.

Signed-off-by: Rany Hany <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20700
Signed-off-by: Robert Marko <[email protected]>