drm/vc4: Convert existing documentation to actual kerneldoc.

I'm going to hook vc4 up to the sphinx build, so clean up its comments
to not generate warnings when we do.

Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170227201144.10970-2-eric@anholt.net
diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
index e328cb86..160f981 100644
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -1453,8 +1453,9 @@
 }
 
 /**
- * Exposes clocks generated by the analog PHY that are consumed by
- * CPRMAN (clk-bcm2835.c).
+ * vc4_dsi_init_phy_clocks - Exposes clocks generated by the analog
+ * PHY that are consumed by CPRMAN (clk-bcm2835.c).
+ * @dsi: DSI encoder
  */
 static int
 vc4_dsi_init_phy_clocks(struct vc4_dsi *dsi)