anv: Rework fences

anv: Rework fences

Our previous fence implementation was very simple.  Fences had two states:
signaled and unsignaled.  However, this didn't properly handle all of the
edge-cases that we need to handle.  In order to handle the case where the
client calls vkGetFenceStatus on a fence that has not yet been submitted
via vkQueueSubmit, we need a three-status system.  In order to handle the
case where the client calls vkWaitForFences on fences which have not yet
been submitted, we need more complex logic and a condition variable.  It's
rather annoying but, so long as the client doesn't do that, we should still
hit the fast path and use i915_gem_wait to do all our waiting.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Cc: "13.0" <mesa-stable@lists.freedesktop.org>