media: cec: disable the hardware when unregistered

When the device is being unregistered disable the hardware, don't wait
until cec_delete_adapter is called as the hardware may have disappeared by
then. This would be the case for hotplugable devices.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reported-by: Bård Eirik Winther <bwinther@cisco.com>
Tested-by: Bård Eirik Winther <bwinther@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>