regulator: palmas: Fix calculating selector in palmas_map_voltage_ldo

This patch fixes below issues when choosing selector:

1. Current code returns negative selector if min_uV < 900000 which is wrong.
   For example, it is possible to satisfy the request with selector = 1 if
   the requested min_uV is 850000.
2. Current code may select a voltage lower than requested min_uV.
   For example, if the requested min_uV is 945000, current code chooses
   selector = 1 which is lower than requested min_uV.
   DIV_ROUND_UP to avoid this case.
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/palmas-regulator.c

@@ -486,9 +486,12 @@ static int palmas_map_voltage_ldo(struct regulator_dev *rdev,
 {
 	int ret, voltage;
 
-	ret = ((min_uV - 900000) / 50000) + 1;
-	if (ret < 0)
-		return ret;
+	if (min_uV == 0)
+		return 0;
+
+	if (min_uV < 900000)
+		min_uV = 900000;
+	ret = DIV_ROUND_UP(min_uV - 900000, 50000) + 1;
 
 	/* Map back into a voltage to verify we're still in bounds */
 	voltage = palmas_list_voltage_ldo(rdev, ret);