regulator: da9052: Ensure enough delay time for .set_voltage_time_sel

Use DIV_ROUND_UP to prevent truncation by integer division issue.
This ensures we return enough delay time.

Also fix returning negative value when new_sel < old_sel.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Link: https://lore.kernel.org/r/20210618141412.4014912-1-axel.lin@ingics.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/da9052-regulator.c

@@ -250,7 +250,8 @@ static int da9052_regulator_set_voltage_time_sel(struct regulator_dev *rdev,
 	case DA9052_ID_BUCK3:
 	case DA9052_ID_LDO2:
 	case DA9052_ID_LDO3:
-		ret = (new_sel - old_sel) * info->step_uV / 6250;
+		ret = DIV_ROUND_UP(abs(new_sel - old_sel) * info->step_uV,
+				   6250);
 		break;
 	}