[media] v4l: add 'unordered' flag to format description ioctl

[media] v4l: add 'unordered' flag to format description ioctl

For explicit synchronization it important for userspace to know if the
format being used by the driver can deliver the buffers back to
userspace
in the same order they were queued with QBUF.

Ordered streams fits nicely in a pipeline with DRM for example, where
ordered buffer are expected.

v2	- Improve documentation (Hans)

Change-Id: I5f0361407c7e50cf7eadb754bc977ed28de87527
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Janghyuck Kim <janghyuck.kim@samsung.com>