media: vivid: Introduce VIDEO_VIVID_OSD

vivid-osd depends on CONFIG_FB, which can be a large dependency. Introduce
CONFIG_VIDEO_VIVID_OSD to control enabling support for testing output
overlay.

Suggested-by: Slawomir Rosek <srosek@google.com>
Co-developed-by: Slawomir Rosek <srosek@google.com>
Signed-off-by: Slawomir Rosek <srosek@google.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
[hverkuil: add newline to squash checkpatch warning]