iio: temperature: tmp117: add support for vcc-supply

Add support to specify the VCC supply which is required to power the
device. According the datasheet 7.3.1 Power Up, the device needs 1.5ms
after the supply voltage reaches the operating range before the
communcation can begin.

Signed-off-by: Thomas Haemmerle <[e-mail]>
Signed-off-by: Marco Felsch <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/temperature/tmp117.c

···
  * Note: This driver assumes that the sensor has been calibrated beforehand.
  */
 
+#include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
···
 #include <linux/kernel.h>
 #include <linux/limits.h>
 #include <linux/property.h>
+#include <linux/regulator/consumer.h>
 
 #include <linux/iio/iio.h>
 
···
 	struct tmp117_data *data;
 	struct iio_dev *indio_dev;
 	int dev_id;
+	int ret;
 
 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
 		return -EOPNOTSUPP;
+
+	ret = devm_regulator_get_enable(&client->dev, "vcc");
+	if (ret)
+		return ret;
+
+	fsleep(1500);
 
 	dev_id = i2c_smbus_read_word_swapped(client, TMP117_REG_DEVICE_ID);
 	if (dev_id < 0)