regulator: twl: Fix the formula to calculate vsel and voltage for twl6030ldo

In twl6030ldo_set_voltage, current code use below formula to calculate vsel:
        vsel = (min_uV/1000 - 1000)/100 + 1;
This is worng because when min_uV is 1000000 uV, vsel is 1.
It should be 0 in this case.
Fix it by change the equation to: (This equation is common for linear mapping)
        vsel = DIV_ROUND_UP(min_uV - rdev->desc->min_uV, rdev->desc->uV_step);

In twl6030ldo_get_voltage, current code use below formula to calculate voltage:
        mV = 1000mv + 100mv * (vsel - 1)
This is worng because when vsel is 0, mV is 900mV. Note the min_uV is 1000mV.
Fix it by change the equation to: (This equation is common for linear mapping)
        return rdev->desc->min_uV + vsel * rdev->desc->uV_step;

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

drivers/regulator/twl-regulator.c

@@ -569,30 +569,21 @@ twl6030ldo_set_voltage(struct regulator_dev *rdev, int min_uV, int max_uV,
 	if ((min_uV/1000 < info->min_mV) || (max_uV/1000 > info->max_mV))
 		return -EDOM;
 
-	/*
-	 * Use the below formula to calculate vsel
-	 * mV = 1000mv + 100mv * (vsel - 1)
-	 */
-	vsel = (min_uV/1000 - 1000)/100 + 1;
+	vsel = DIV_ROUND_UP(min_uV - rdev->desc->min_uV, rdev->desc->uV_step);
 	*selector = vsel;
-	return twlreg_write(info, TWL_MODULE_PM_RECEIVER, VREG_VOLTAGE, vsel);
 
+	return twlreg_write(info, TWL_MODULE_PM_RECEIVER, VREG_VOLTAGE, vsel);
 }
 
 static int twl6030ldo_get_voltage(struct regulator_dev *rdev)
 {
 	struct twlreg_info	*info = rdev_get_drvdata(rdev);
-	int		vsel = twlreg_read(info, TWL_MODULE_PM_RECEIVER,
-								VREG_VOLTAGE);
+	int vsel = twlreg_read(info, TWL_MODULE_PM_RECEIVER, VREG_VOLTAGE);
 
 	if (vsel < 0)
 		return vsel;
 
-	/*
-	 * Use the below formula to calculate vsel
-	 * mV = 1000mv + 100mv * (vsel - 1)
-	 */
-	return (1000 + (100 * (vsel - 1))) * 1000;
+	return rdev->desc->min_uV + vsel * rdev->desc->uV_step;
 }
 
 static struct regulator_ops twl6030ldo_ops = {