drm/i915: pass seqno to i915_hangcheck_ring_idle

In preparation for next commit, pass seqno as a parameter
to i915_hangcheck_ring_idle as it will be used inside
i915_hangcheck_elapsed.

Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>