drm/i915: Add kerneldoc for intel_pipe_update_{start, end}
Note that a later patch will use these functions in some other file
and drop the static. Hence the kerneldoc looks appropriate.
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com> Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
[danvet: Add comment that the functions will become non-static
shortly.] Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>