[media] v4l: vsp1: Document the vsp1_pipeline structure

/*

 * struct vsp1_pipeline - A VSP1 hardware pipeline

 * @media: the media pipeline

 * @pipe: the media pipeline

 * @irqlock: protects the pipeline state

 * @state: current state

 * @wq: work queue to wait for state change completion

 * @frame_end: frame end interrupt handler

 * @lock: protects the pipeline use count and stream count

 * @use_count: number of video nodes using the pipeline

 * @stream_count: number of streaming video nodes

 * @buffers_ready: bitmask of RPFs and WPFs with at least one buffer available

 * @num_inputs: number of RPFs

 * @inputs: array of RPFs in the pipeline

 * @output: WPF at the output of the pipeline

 * @bru: BRU entity, if present

 * @lif: LIF entity, if present

 * @uds: UDS entity, if present

 * @uds_input: entity at the input of the UDS, if the UDS is present

 * @entities: list of entities in the pipeline

 */

struct vsp1_pipeline {

	struct media_pipeline pipe;