mfd/bus: sunxi-rsb: Make .remove() callback return void

The driver core ignores the return value of struct device_driver::remove
because there is only little that can be done. To simplify the quest to
make this function return void, let struct sunxi_rsb_driver::remove
return void, too. All users already unconditionally return 0, this
commit makes this obvious and ensures future users don't behave
differently. To simplify even further, make axp20x_device_remove()
return void instead of returning 0 unconditionally, too.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/axp20x-rsb.c b/drivers/mfd/axp20x-rsb.c
index 4cdc79f..214bc0d 100644
--- a/drivers/mfd/axp20x-rsb.c
+++ b/drivers/mfd/axp20x-rsb.c
@@ -49,11 +49,11 @@ static int axp20x_rsb_probe(struct sunxi_rsb_device *rdev)
 	return axp20x_device_probe(axp20x);
 }
 
-static int axp20x_rsb_remove(struct sunxi_rsb_device *rdev)
+static void axp20x_rsb_remove(struct sunxi_rsb_device *rdev)
 {
 	struct axp20x_dev *axp20x = sunxi_rsb_device_get_drvdata(rdev);
 
-	return axp20x_device_remove(axp20x);
+	axp20x_device_remove(axp20x);
 }
 
 static const struct of_device_id axp20x_rsb_of_match[] = {