regulator: s5m8767: Use DIV_ROUND_UP to calculate selector

Integer division may truncate the result.
Use DIV_ROUND_UP to ensure new voltage setting falls within specified range.

Also properly handle the case min_vol < desc->min to ensure we don't return
negative value for selector.

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

drivers/regulator/s5m8767.c

@@ -347,7 +347,10 @@ static int s5m8767_convert_voltage_to_sel(
 	if (max_vol < desc->min || min_vol > desc->max)
 		return -EINVAL;
 
-	selector = (min_vol - desc->min) / desc->step;
+	if (min_vol < desc->min)
+		min_vol = desc->min;
+
+	selector = DIV_ROUND_UP(min_vol - desc->min, desc->step);
 
 	if (desc->min + desc->step * selector > max_vol)
 		return -EINVAL;