drm/i915: Propagate error from completed fences

drm/i915: Propagate error from completed fences

We need to preserve fatal errors from fences that are being terminated
as we hook them up.

Fixes: 605804afa3b1 ("drm/i915: Propagate fence errors")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200506162136.3325-1-chris@chris-wilson.co.uk
(cherry picked from commit 24fe5f2ab2478053d50a3bc629ada895903a5cbc)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>