WPS: Fix strict validation to mandate Network Index attribute

While this attribute is is now deprecated, it is still required
for backwards compatibility. Better check this if strict validation
is enabled.

src/wps/wps_validate.c

@@ -1037,7 +1037,7 @@ static int wps_validate_cred(const u8 *cred, size_t len)
 		return -1;
 	}
 
-	if (wps_validate_network_idx(attr.network_idx, 0) ||
+	if (wps_validate_network_idx(attr.network_idx, 1) ||
 	    wps_validate_ssid(attr.ssid, attr.ssid_len, 1) ||
 	    wps_validate_auth_type(attr.auth_type, 1) ||
 	    wps_validate_encr_type(attr.encr_type, 1) ||