Ring switches can occur many times per frame, and are often out of
control, causing frequent RPS boosting for no practical benefit. Treat
the sw semaphore synchronisation as a separate client and only allow it
to boost once per busy/idle cycle.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
[danvet: s/rq/req/]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>