Input: wm97xx-core - report a phys for WM97xx touchscreens

phys is displayed in diagnostic output like that from evbug so ensure
that it is set to something.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/touchscreen/wm97xx-core.c

@@ -616,6 +616,7 @@ static int wm97xx_probe(struct device *dev)
 
 	/* set up touch configuration */
 	wm->input_dev->name = "wm97xx touchscreen";
+	wm->input_dev->phys = "wm97xx";
 	wm->input_dev->open = wm97xx_ts_input_open;
 	wm->input_dev->close = wm97xx_ts_input_close;
 	set_bit(EV_ABS, wm->input_dev->evbit);