Convert this driver to use struct v4l2_fh and as a result switch to
using vb2/v4l2_mem2mem helper functions as well.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>