drm/i915/gt: Add arbitration check before semaphore wait

Similar to commit 49b20dbf

 ("drm/i915/gt: Perform an arbitration
check before busywaiting"), also add a check prior to the busywait
on gen8+, as we have now seen (because we added a selftest to add fault
injection into the engine resets) the same engine reset failure leading
to an indefinite wait on the ring-stop semaphore. So not a Tigerlake
specific bug after all, though it still seems odd behaviour for the
busywait as we do get the arbitration point elsewhere on a miss.

Testcase: igt_reset_fail_engine
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/20210117110418.3361-1-chris@chris-wilson.co.uk