regulator: core: Factor out regulator_map_voltage

_regulator_call_set_voltage has code to translate a minimum/maximum
voltage pair into a selector. This code is useful for others aswell,
so create a regulator_map_voltage function.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -2606,6 +2606,23 @@ int regulator_is_supported_voltage(struct regulator *regulator,
 }
 EXPORT_SYMBOL_GPL(regulator_is_supported_voltage);
 
+static int regulator_map_voltage(struct regulator_dev *rdev, int min_uV,
+				 int max_uV)
+{
+	const struct regulator_desc *desc = rdev->desc;
+
+	if (desc->ops->map_voltage)
+		return desc->ops->map_voltage(rdev, min_uV, max_uV);
+
+	if (desc->ops->list_voltage == regulator_list_voltage_linear)
+		return regulator_map_voltage_linear(rdev, min_uV, max_uV);
+
+	if (desc->ops->list_voltage == regulator_list_voltage_linear_range)
+		return regulator_map_voltage_linear_range(rdev, min_uV, max_uV);
+
+	return regulator_map_voltage_iterate(rdev, min_uV, max_uV);
+}
+
 static int _regulator_call_set_voltage(struct regulator_dev *rdev,
 				       int min_uV, int max_uV,
 				       unsigned *selector)
@@ -2694,23 +2711,7 @@ static int _regulator_do_set_voltage(struct regulator_dev *rdev,
 		}
 
 	} else if (rdev->desc->ops->set_voltage_sel) {
-		if (rdev->desc->ops->map_voltage) {
-			ret = rdev->desc->ops->map_voltage(rdev, min_uV,
-							   max_uV);
-		} else {
-			if (rdev->desc->ops->list_voltage ==
-			    regulator_list_voltage_linear)
-				ret = regulator_map_voltage_linear(rdev,
-								min_uV, max_uV);
-			else if (rdev->desc->ops->list_voltage ==
-				 regulator_list_voltage_linear_range)
-				ret = regulator_map_voltage_linear_range(rdev,
-								min_uV, max_uV);
-			else
-				ret = regulator_map_voltage_iterate(rdev,
-								min_uV, max_uV);
-		}
-
+		ret = regulator_map_voltage(rdev, min_uV, max_uV);
 		if (ret >= 0) {
 			best_val = rdev->desc->ops->list_voltage(rdev, ret);
 			if (min_uV <= best_val && max_uV >= best_val) {