Add missing mutex_destroy() call in iio_dev_release() to properly
clean up the mutex initialized in iio_device_alloc(). Ensure proper
resource cleanup and follows kernel practices.

Found by code review.

While at it, create a lockdep key before mutex initialisation.
This will help with converting it to the better API in the future.

Fixes: 847ec80bbaa7 ("Staging: IIO: core support for device registration and management")
Fixes: ac917a81117c ("staging:iio:core set the iio_dev.info pointer to null on unregister under lock.")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/iio/industrialio-core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 88c3d585a1bd..93d6e5b101cf 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -1654,6 +1654,9 @@ static void iio_dev_release(struct device *device)
 
 	iio_device_detach_buffers(indio_dev);
 
+	mutex_destroy(&iio_dev_opaque->info_exist_lock);
+	mutex_destroy(&iio_dev_opaque->mlock);
+
 	lockdep_unregister_key(&iio_dev_opaque->mlock_key);
 
 	ida_free(&iio_ida, iio_dev_opaque->id);
@@ -1698,8 +1701,7 @@ struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv)
 	indio_dev->dev.type = &iio_device_type;
 	indio_dev->dev.bus = &iio_bus_type;
 	device_initialize(&indio_dev->dev);
-	mutex_init(&iio_dev_opaque->mlock);
-	mutex_init(&iio_dev_opaque->info_exist_lock);
+
 	INIT_LIST_HEAD(&iio_dev_opaque->channel_attr_list);
 
 	iio_dev_opaque->id = ida_alloc(&iio_ida, GFP_KERNEL);
@@ -1722,6 +1724,9 @@ struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv)
 	lockdep_register_key(&iio_dev_opaque->mlock_key);
 	lockdep_set_class(&iio_dev_opaque->mlock, &iio_dev_opaque->mlock_key);
 
+	mutex_init(&iio_dev_opaque->mlock);
+	mutex_init(&iio_dev_opaque->info_exist_lock);
+
 	return indio_dev;
 }
 EXPORT_SYMBOL(iio_device_alloc);
-- 
2.50.1