media: cx231xx: convert to the vb2 framework

This patch converts the cx231xx driver to the vb2 framework.
Since you can't do a partial conversion this is a big-bang patch,
i.e. large and hard to review. I never found a way around this.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Co-developed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>