drm/v3d: Update a comment about what uses v3d_job_dependency().

I merged bin and render's paths in a late refactoring.

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20181108161654.19888-3-eric@anholt.net
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>