media: cedrus: Cleanup duplicate declarations from cedrus_dec header

Some leftover declarations are still in the cedrus_dec header although
they were moved to cedrus_video already. Clean them up.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>