drm: rcar-du: Fix rcar_du_crtc structure documentation

The rcar_du_crtc structure index field contains the CRTC hardware index,
not the hardware and software index. Update the documentation
accordingly.

Fixes: 5361cc7f ("drm: rcar-du: Split CRTC handling to support hardware indexing")
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_crtc.h

@@ -27,7 +27,7 @@ struct rcar_du_vsp;
  * @clock: the CRTC functional clock
  * @extclock: external pixel dot clock (optional)
  * @mmio_offset: offset of the CRTC registers in the DU MMIO block
- * @index: CRTC software and hardware index
+ * @index: CRTC hardware index
  * @initialized: whether the CRTC has been initialized and clocks enabled
  * @dsysr: cached value of the DSYSR register
  * @vblank_enable: whether vblank events are enabled on this CRTC