regulator: wm831x-ldo: Use regulator_map_voltage_linear for wm831x_alive_ldo_ops

wm831x_alive_ldo_ops uses simple linear voltage maps.
Thus use regulator_map_voltage_linear is more efficient than using the default
regulator_map_voltage_iterate.
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/wm831x-ldo.c

@@ -690,6 +690,7 @@ static int wm831x_alive_ldo_get_status(struct regulator_dev *rdev)
 
 static struct regulator_ops wm831x_alive_ldo_ops = {
 	.list_voltage = regulator_list_voltage_linear,
+	.map_voltage = regulator_map_voltage_linear,
 	.get_voltage_sel = regulator_get_voltage_sel_regmap,
 	.set_voltage = wm831x_alive_ldo_set_voltage,
 	.set_suspend_voltage = wm831x_alive_ldo_set_suspend_voltage,