We recorded the execlists->queue_priority_hint update for the inflight
request without kicking the tasklet. The next submitted request then
failed to be scheduled as it had a lower priority than the hint, leaving
the HW running with only the inflight request.

Fixes: 6cebcf74 ("drm/i915: Tweak scheduler's kick_submission()")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200519063123.20673-1-chris@chris-wilson.co.uk