staging: media: tegra-video: improve documentation of tegra_video_format fields

Some fields are irrelevant for Tegra20/VIP. Add a note to clarify that.
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

drivers/staging/media/tegra-video/vi.h

@@ -260,11 +260,11 @@ enum tegra_image_dt {
 /**
  * struct tegra_video_format - Tegra video format description
  *
- * @img_dt: image data type
- * @bit_width: format width in bits per component
+ * @img_dt: MIPI CSI-2 data type (for CSI-2 only)
+ * @bit_width: format width in bits per component (for CSI/Tegra210 only)
  * @code: media bus format code
  * @bpp: bytes per pixel (when stored in memory)
- * @img_fmt: image format
+ * @img_fmt: image format (for CSI/Tegra210 only)
  * @fourcc: V4L2 pixel format FCC identifier
  */
 struct tegra_video_format {