We need to get folks to run

$ make htmldocs

more often and actually check the output. With the fancy new sphinx
stuff there's hopefully no more excuses.

Fixes: 286dbb8d ("drm/atomic: Rename async parameter to nonblocking.")
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1464729075-22243-4-git-send-email-daniel.vetter@ffwll.ch