regulator: Convert mc13xxx regulator drivers to set_voltage_sel

Convert mc13892_sw_regulator_ops and mc13xxx_regulator_ops to set_voltage_sel.
mc13xxx_get_best_voltage_index function is not used now, remove it.

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

drivers/regulator/mc13xxx.h

@@ -35,8 +35,6 @@ struct mc13xxx_regulator_priv {
 
 extern int mc13xxx_sw_regulator(struct regulator_dev *rdev);
 extern int mc13xxx_sw_regulator_is_enabled(struct regulator_dev *rdev);
-extern int mc13xxx_get_best_voltage_index(struct regulator_dev *rdev,
-						int min_uV, int max_uV);
 extern int mc13xxx_regulator_list_voltage(struct regulator_dev *rdev,
 						unsigned selector);
 extern int mc13xxx_fixed_regulator_set_voltage(struct regulator_dev *rdev,