media: staging: media: rkvdec: Update TODO list

VP9 support has been added to the driver by commit f25709c4
("media: rkvdec: Add the VP9 backend").
And the VP9 uABI was merged with commit b88dbe38
("media: uapi: Add VP9 stateless decoder controls").

The remaining codec that keeps this driver in staging is HEVC.
Update the TODO list accordingly.

Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>