drm-sync timeline signaling

[Lionel Landwerlin]

Hi all,

While picking up the IGT tests for timeline syncobj,
I noticed that although we deal with multi wait across both timeline 
(with point value > 0) and binary (point value = 0) syncobjs,
we don't seem to have a similar behavior with signaling.

Do you have any thought on this?
I'm considering writing some docs but I'm not quite sure whether this 
difference between signaling/waiting was intentional or just overlooked.

Thanks,

-Lionel