Revert "Staging: iio: adt7316: Add an extra check for 'ret' equals to 0"

This reverts commit 00426e99789357dbff7e719a092ce36a3ce49d94.

i2c_smbus_read_byte() returns 0 when a byte with the value 0 is read from
the device. This is a valid read so revert the check for 0.

Signed-off-by: Jeremy Fertic <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/staging/iio/addac/adt7316-i2c.c

···
 	}
 
 	ret = i2c_smbus_read_byte(client);
-
-	if (!ret)
-		return -EIO;
-
 	if (ret < 0) {
 		dev_err(&cl->dev, "I2C read error\n");
 		return ret;