regulator: Only notify voltage changes when they succeed

Currently we notify a voltage change whenever we exit set_voltage(),
even if the change failed for some reason (eg, a constraints issue).
This shouldn't cause any substantial ill effects but is wasteful as
listeners get notified on noops. Fix this by moving the notification
into _do_set_voltage() and only notifying if we don't return an error.
Reported-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

drivers/regulator/core.c

@@ -1667,6 +1667,10 @@ static int _regulator_do_set_voltage(struct regulator_dev *rdev,
 		ret = -EINVAL;
 	}
 
+	if (ret == 0)
+		_notifier_call_chain(rdev, REGULATOR_EVENT_VOLTAGE_CHANGE,
+				     NULL);
+
 	trace_regulator_set_voltage_complete(rdev_get_name(rdev), selector);
 
 	return ret;
@@ -1718,7 +1722,6 @@ int regulator_set_voltage(struct regulator *regulator, int min_uV, int max_uV)
 	ret = _regulator_do_set_voltage(rdev, min_uV, max_uV);
 
 out:
-	_notifier_call_chain(rdev, REGULATOR_EVENT_VOLTAGE_CHANGE, NULL);
 	mutex_unlock(&rdev->mutex);
 	return ret;
 }