regulator: max77686: Use regulator_map_voltage_linear for simple linear mappings

Both max77686_ops and max77686_buck_dvs_ops use simple linear voltage maps.
Thus use regulator_map_voltage_linear is more efficient than using the defult
regulator_map_voltage_iterate.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/max77686.c

@@ -90,6 +90,7 @@ static int max77686_set_voltage_time_sel(struct regulator_dev *rdev,
 
 static struct regulator_ops max77686_ops = {
 	.list_voltage		= regulator_list_voltage_linear,
+	.map_voltage		= regulator_map_voltage_linear,
 	.is_enabled		= regulator_is_enabled_regmap,
 	.enable			= regulator_enable_regmap,
 	.disable		= regulator_disable_regmap,
@@ -100,6 +101,7 @@ static struct regulator_ops max77686_ops = {
 
 static struct regulator_ops max77686_buck_dvs_ops = {
 	.list_voltage		= regulator_list_voltage_linear,
+	.map_voltage		= regulator_map_voltage_linear,
 	.is_enabled		= regulator_is_enabled_regmap,
 	.enable			= regulator_enable_regmap,
 	.disable		= regulator_disable_regmap,