mei: bus: don't clean driver pointer

It's not needed to set driver to NULL in mei_cl_device_remove()
which is bus_type remove() handler as this is done anyway
in __device_release_driver().

Actually this is causing an endless loop in driver_detach()
on ubuntu patched kernel, while removing (rmmod) the mei_hdcp module.
The reason list_empty(&drv->p->klist_devices.k_list) is always not-empty.
as the check is always true in  __device_release_driver()
	if (dev->driver != drv)
		return;

The non upstream patch is causing this behavior, titled:
'vfio -- release device lock before userspace requests'

Nevertheless the fix is correct also for the upstream.

Link: https://patchwork.ozlabs.org/project/ubuntu-kernel/patch/[email protected]/
Cc: <[email protected]>
Cc: Andy Whitcroft <[email protected]>
Signed-off-by: Alexander Usyskin <[email protected]>
Signed-off-by: Tomas Winkler <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: ausyskin

drivers/misc/mei/bus.c

@@ -745,9 +745,8 @@ static int mei_cl_device_remove(struct device *dev)
 
 	mei_cl_bus_module_put(cldev);
 	module_put(THIS_MODULE);
-	dev->driver = NULL;
-	return ret;
 
+	return ret;
 }
 
 static ssize_t name_show(struct device *dev, struct device_attribute *a,