[media] v4l: Add multi-planar API definitions to the V4L2 API

Multi-planar API is as a backwards-compatible extension of the V4L2 API,
which allows video buffers to consist of one or more planes. Planes are
separate memory buffers; each has its own mapping, backed by usually
separate physical memory buffers.

Many different uses for the multi-planar API are possible, examples
include:
- embedded devices requiring video components to be placed in physically
separate buffers, e.g. for Samsung S3C/S5P SoC series' video codec,
Y and interleaved Cb/Cr components reside in buffers in different
memory banks;
- applications may receive (or choose to store) video data of one video
buffer in separate memory buffers; such data would have to be temporarily
copied together into one buffer before passing it to a V4L2 device;
- applications or drivers may want to pass metadata related to a buffer and
it may not be possible to place it in the same buffer, together with video
data.

[mchehab@redhat.com: CodingStyle fixes]
Signed-off-by: Pawel Osciak <p.osciak@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>