cec: add cec_adapter to cec_notifier_cec_adap_unregister()

It is possible for one HDMI connector to have multiple CEC adapters. The
typical real-world scenario is that where one adapter is used when the
device is in standby, and one that's better/smarter when the device is
powered up.

The cec-notifier changes were made with that in mind, but I missed that in
order to support this you need to tell cec_notifier_cec_adap_unregister()
which adapter you are unregistering from the notifier.

Add this additional argument. It is currently unused, but once all drivers
use this, the CEC core will be adapted for these use-cases.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/e9fc8740-6be6-43a7-beee-ce2d7b54936e@xs4all.nl