drm/i915: Double check hangcheck.seqno after reset

Check that there was not a late recovery between us declaring the GPU
hung and processing the reset. If the GPU did recover by itself, let the
request remain on the active list and see if it hangs again!

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161004201132.21801-5-chris@chris-wilson.co.uk