USB: ldusb: fix memleak on disconnect

USB: ldusb: fix memleak on disconnect

commit b14a39048c1156cfee76228bf449852da2f14df8 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: 2824bd250f0b ("[PATCH] USB: add ldusb driver")
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191010125835.27031-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>