regulator: tps51632: Fix setting ramp delay

According to the datasheet:

SLEW Register(Address = 07h)
b7      b6      b5      b4      b3      b2      b1      b0
48mV/us 42mV/us 36mV/us 30mV/us 24mV/us 18mV/us 12mV/us 6mV/us

Current code does not set correct slew rate in some cases:
e.g. Assume ramp_delay is 10000, current code sets slew register to 6mV/us.
Fix the logic to set slew register.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/tps51632-regulator.c

@@ -94,11 +94,14 @@ static int tps51632_dcdc_set_ramp_delay(struct regulator_dev *rdev,
 		int ramp_delay)
 {
 	struct tps51632_chip *tps = rdev_get_drvdata(rdev);
-	int bit = ramp_delay/6000;
+	int bit;
 	int ret;
 
-	if (bit)
-		bit--;
+	if (ramp_delay == 0)
+		bit = 0;
+	else
+		bit = DIV_ROUND_UP(ramp_delay, 6000) - 1;
+
 	ret = regmap_write(tps->regmap, TPS51632_SLEW_REGS, BIT(bit));
 	if (ret < 0)
 		dev_err(tps->dev, "SLEW reg write failed, err %d\n", ret);