Since amalgamating the queued and active lists in commit 422d7df4
("drm/i915: Replace engine->timeline with a plain list"), performing a
i915_request_submit() will remove the request from the execlists
priority queue.

References: 422d7df4 ("drm/i915: Replace engine->timeline with a plain list")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190923110056.15176-2-chris@chris-wilson.co.uk