USB: legousbtower: fix memleak on disconnect

USB: legousbtower: fix memleak on disconnect

commit b6c03e5f7b463efcafd1ce141bd5a8fc4e583ae2 upstream.

If disconnect() races with release() after a process has been
interrupted, release() could end up returning early and the driver would
fail to free its driver data.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191010125835.27031-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>