gpio: mpc8xxx: Fix wakeup source leaks on device unbind

Device can be unbound, so driver must also release memory for the wakeup
source.

Cc: [e-mail]
Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-mpc8xxx.c

···
 		goto err;
 	}
 
-	device_init_wakeup(dev, true);
+	ret = devm_device_init_wakeup(dev);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to init wakeup\n");
 
 	return 0;
 err: