[media] s5p-fimc: Remove v4l2_device from video capture and m2m driver

Currently there is a v4l2_device instance being registered per each
(capture and memory-to-memory) video node created per FIMC H/W instance.
This patch is a prerequisite for using the top level v4l2_device
instantiated by the media device driver.
To retain current debug trace semantic (so it's possible to distinguish
between the capture and m2m FIMC) the video_device is used in place
of v4l2_device where appropriate.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>