driver core: dd: remove deferred_devices variable

driver core: dd: remove deferred_devices variable

No need to save the debugfs dentry for the "devices_deferred" debugfs
file (gotta love the juxtaposition), if we need to remove it we can look
it up from debugfs itself.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20210216142400.3759099-2-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>