This series adds a deadline hint to fences, so realtime deadlines
such as vblank can be communicated to the fence signaller for power/
frequency management decisions.

This is partially inspired by a trick i915 does, but implemented
via dma-fence for a couple of reasons:

1) To continue to be able to use the atomic helpers
2) To support cases where display and gpu are different drivers

See https://patchwork.freedesktop.org/series/93035/

This does not yet add any UAPI, although this will be needed in
a number of cases:

1) Workloads "ping-ponging" between CPU and GPU, where we don't
   want the GPU freq governor to interpret time stalled waiting
   for GPU as "idle" time
2) Cases where the compositor is waiting for fences to be signaled
   before issuing the atomic ioctl, for example to maintain 60fps
   cursor updates even when the GPU is not able to maintain that
   framerate.
Signed-off-by: Rob Clark <robdclark@chromium.org>