device: add debug prints for mode switching

Its useful to know when the device has switched modes

src/device.c

@@ -2065,6 +2065,8 @@ static struct l_dbus_message *device_set_mode_ap(struct device *device,
 			device->state != DEVICE_STATE_AUTOCONNECT)
 		return dbus_error_busy(message);
 
+	l_debug("");
+
 	periodic_scan_stop(device);
 
 	/* Drop all state we can related to client mode */
@@ -2106,6 +2108,8 @@ static struct l_dbus_message *device_set_mode_sta(struct device *device,
 
 	ap_remove_interface(device);
 
+	l_debug("");
+
 	return NULL;
 }