video: Fix video sync kernel-doc format

Place description below function parameters to make kernel-doc stript
happy. Also rename dev to vid to be aligned with function parameters.

Fixes: 1acafc73 ("dm: video: Add a video uclass")
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>