device: fix emitting unnecessary PROP_IFINDEX notification in NMDevice

Fixes: ea1f0fc0a6 ('device: let NMDevice track a NML3Cfg instance for each ifindex')

src/devices/nm-device.c

@@ -1806,7 +1806,9 @@ _set_ifindex (NMDevice *self, int ifindex, gboolean is_ip_ifindex)
 	       NM_PRINT_FMT_QUOTED (l3cfg_old, " (old-l3cfg: ", nm_hash_obfuscated_ptr_str_a (l3cfg_old), ")", ""),
 	       NM_PRINT_FMT_QUOTED (*p_l3cfg, " (l3cfg: ", nm_hash_obfuscated_ptr_str_a (*p_l3cfg), ")", ""));
 
+	if (!is_ip_ifindex)
 		_notify (self, PROP_IFINDEX);
+
 	return TRUE;
 }