drm/i915: store ring hangcheck action

For guilty batchbuffer analysis later on when rings are reset,
store what state the ring was on when hang was declared.
This helps to weed out the waiting rings from the active ones.

Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>