staging:iio:adis16080: Remove unnecessary lock

All sections in which the transfer buffer is accessed are already protected by
the IIO device's mlock. So we do not need the extra mutex protecting the buffer.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/gyro/adis16080_core.c

@@ -33,11 +33,9 @@
  * struct adis16080_state - device instance specific data
  * @us:			actual spi_device to write data
  * @buf:		transmit or receive buffer
- * @buf_lock:		mutex to protect tx and rx
  **/
 struct adis16080_state {
 	struct spi_device		*us;
-	struct mutex			buf_lock;
 
 	__be16 buf ____cacheline_aligned;
 };
@@ -59,7 +57,6 @@ static int adis16080_read_sample(struct iio_dev *indio_dev,
 		},
 	};
 
-	mutex_lock(&st->buf_lock);
 	st->buf = cpu_to_be16(addr | ADIS16080_DIN_WRITE);
 
 	spi_message_init(&m);
@@ -69,7 +66,6 @@ static int adis16080_read_sample(struct iio_dev *indio_dev,
 	ret = spi_sync(st->us, &m);
 	if (ret == 0)
 		*val = sign_extend32(be16_to_cpu(st->buf), 11);
-	mutex_unlock(&st->buf_lock);
 
 	return ret;
 }
@@ -144,7 +140,6 @@ static int adis16080_probe(struct spi_device *spi)
 
 	/* Allocate the comms buffers */
 	st->us = spi;
-	mutex_init(&st->buf_lock);
 
 	indio_dev->name = spi->dev.driver->name;
 	indio_dev->channels = adis16080_channels;