regulator: ad5398: Fix return value of ad5398_write_reg

i2c_master_send() returns the number of bytes written on success.
So current code returns 2 if ad5398_write_reg() success.
This return value is propagated to .set_current_limit, .enable and .disable
callbacks of regulator_ops. This can be a problem, for example, if the
users test if the return value of regulator_set_current_limit() is 0.
Fix it by making ad5398_write_reg() return 0 on success.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/ad5398.c

@@ -58,10 +58,12 @@ static int ad5398_write_reg(struct i2c_client *client, const unsigned short data
 
 	val = cpu_to_be16(data);
 	ret = i2c_master_send(client, (char *)&val, 2);
-	if (ret < 0)
+	if (ret != 2) {
 		dev_err(&client->dev, "I2C write error\n");
+		return ret < 0 ? ret : -EIO;
+	}
 
-	return ret;
+	return 0;
 }
 
 static int ad5398_get_current_limit(struct regulator_dev *rdev)