A client which is ready, but hasn't run for a while, should receive
the same benefit as one which has simply been idle for a while. Use
the smart_stop_tick to see how long it has been since a client has
run instead of smart_check_tick, which got reset each time a client
was ready, even if it didn't get to run.
Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Keith Packard <keithp@keithp.com>
Tested-by: Chris Wilson <chris@chris-wilson.co.uk>