mfd: wm831x: Fix possible NULL pointer dereference

The driver always checks for pdata being NULL except in one place.
Add a check to prevent a possible NULL pointer deference error.

Signed-off-by: Javier Martinez Canillas <[e-mail]>
Acked-by: Charles Keepax <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/wm831x-core.c

···
 	mutex_init(&wm831x->io_lock);
 	mutex_init(&wm831x->key_lock);
 	dev_set_drvdata(wm831x->dev, wm831x);
-	wm831x->soft_shutdown = pdata->soft_shutdown;
+
+	if (pdata)
+		wm831x->soft_shutdown = pdata->soft_shutdown;
 
 	ret = wm831x_reg_read(wm831x, WM831X_PARENT_ID);
 	if (ret < 0) {