nfit: acpi_nfit_notify(): Do not leave device locked

nfit: acpi_nfit_notify(): Do not leave device locked

Orabug: 22913653

Even if dev->driver is null because we are being removed,
it is safer to not leave device locked.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
(cherry picked from commit d91e892825ae6f0ed4f8b07ae5d348eff86ab2ea)
Signed-off-by: Dan Duval <dan.duval@oracle.com>