wpa_supplicant: start after wireless interfaces

wpa_supplicant fails to start if the wireless interfaces aren't ready yet,
so we need to add a system ordering directive here to start wpa_supplicant
after the interfaces are ready. Note that Requires= is not enough since
it does not imply ordering.

nixos/modules/services/networking/wpa_supplicant.nix

@@ -129,7 +129,7 @@ in {
       in {
         description = "WPA Supplicant";
 
-        after = [ "network-interfaces.target" ];
+        after = [ "network-interfaces.target" ] ++ lib.concatMap deviceUnit ifaces;
         requires = lib.concatMap deviceUnit ifaces;
         wantedBy = [ "network.target" ];