staging: iio: ade7753: replace mlock with driver private lock

Replace driver usage of mlock with driver private lock to meet the new
model where usage of iio_dev->mlock is being redefined as protecting
operating mode changes(changes between BUFFER* and DIRECT modes).
Signed-off-by: Himanshi Jain <himshijain.hj@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/meter/ade7753.c

@@ -81,10 +81,12 @@
  * @tx:         transmit buffer
  * @rx:         receive buffer
  * @buf_lock:       mutex to protect tx and rx
+ * @lock:	protect sensor data
  **/
 struct ade7753_state {
 	struct spi_device   *us;
 	struct mutex        buf_lock;
+	struct mutex	    lock; /* protect sensor data */
 	u8          tx[ADE7753_MAX_TX] ____cacheline_aligned;
 	u8          rx[ADE7753_MAX_RX];
 };
@@ -483,7 +485,7 @@ static ssize_t ade7753_write_frequency(struct device *dev,
 	if (!val)
 		return -EINVAL;
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
 
 	t = 27900 / val;
 	if (t > 0)
@@ -504,7 +506,7 @@ static ssize_t ade7753_write_frequency(struct device *dev,
 	ret = ade7753_spi_write_reg_16(dev, ADE7753_MODE, reg);
 
 out:
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return ret ? ret : len;
 }
@@ -579,6 +581,7 @@ static int ade7753_probe(struct spi_device *spi)
 	st = iio_priv(indio_dev);
 	st->us = spi;
 	mutex_init(&st->buf_lock);
+	mutex_init(&st->lock);
 
 	indio_dev->name = spi->dev.driver->name;
 	indio_dev->dev.parent = &spi->dev;