Track the nearest deadline on a fence timeline and set a timer to expire
shortly before to trigger boost if the fence has not yet been signaled.

v2: rebase
Signed-off-by: Rob Clark <robdclark@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/525816/
Link: https://lore.kernel.org/r/20230308155322.344664-13-robdclark@gmail.com