When parking the engines and their breadcrumbs, if we have waiters left
then they missed their wakeup. Verify that each waiter's seqno did
complete.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180222092545.17216-2-chris@chris-wilson.co.uk