Input: wm97xx - make missing platform data non-fatal

Commit 6480af4 ("power_supply: wm97xx_battery: use
power_supply_get_drvdata") made wm97xx platform data mandatory, although
it's still optional.

This patch fixes an oops during driver probe on one of my MIPS boards with
a wm9712.

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
Reviewed-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/wm97xx-core.c

@@ -682,7 +682,7 @@ static int wm97xx_probe(struct device *dev)
 	}
 	platform_set_drvdata(wm->battery_dev, wm);
 	wm->battery_dev->dev.parent = dev;
-	wm->battery_dev->dev.platform_data = pdata->batt_pdata;
+	wm->battery_dev->dev.platform_data = pdata ? pdata->batt_pdata : NULL;
 	ret = platform_device_add(wm->battery_dev);
 	if (ret < 0)
 		goto batt_reg_err;