parport: plug a sysctl register leak

parport registers two sysctl directories in the parport_proc_register
function but only one of them was getting unregistered in
parport_proc_unregister. Keep track of both sysctl table headers and
handle them together when (un)registering.

Signed-off-by: Joel Granados <j.granados@samsung.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>