iio: gyro: itg3200_core: do not use internal iio_dev lock

The iio_device lock is only meant for internal use. Hence define a
device local lock to protect against concurrent accesses.

While at it, properly include "mutex.h" for mutex related APIs.

Signed-off-by: Nuno Sá <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/gyro/itg3200_core.c

···
 #include <linux/slab.h>
 #include <linux/stat.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/delay.h>
 
 #include <linux/iio/iio.h>
···
 			     int val2,
 			     long mask)
 {
+	struct itg3200 *st = iio_priv(indio_dev);
 	int ret;
 	u8 t;
 
···
 		if (val == 0 || val2 != 0)
 			return -EINVAL;
 
-		mutex_lock(&indio_dev->mlock);
+		mutex_lock(&st->lock);
 
 		ret = itg3200_read_reg_8(indio_dev, ITG3200_REG_DLPF, &t);
 		if (ret) {
-			mutex_unlock(&indio_dev->mlock);
+			mutex_unlock(&st->lock);
 			return ret;
 		}
 		t = ((t & ITG3200_DLPF_CFG_MASK) ? 1000u : 8000u) / val - 1;
···
 					  ITG3200_REG_SAMPLE_RATE_DIV,
 					  t);
 
-		mutex_unlock(&indio_dev->mlock);
+		mutex_unlock(&st->lock);
 		return ret;
 
 	default:
···
 	ret = itg3200_initial_setup(indio_dev);
 	if (ret)
 		goto error_remove_trigger;
+
+	mutex_init(&st->lock);
 
 	ret = iio_device_register(indio_dev);
 	if (ret)

include/linux/iio/gyro/itg3200.h

···
 	struct i2c_client	*i2c;
 	struct iio_trigger	*trig;
 	struct iio_mount_matrix orientation;
+	/* lock to protect against multiple access to the device */
+	struct mutex		lock;
 };
 
 enum ITG3200_SCAN_INDEX {