drm/i915: Introduce ring set_seqno

In preparation for setting per ring initial seqno values
add ring::set_seqno().

Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2 files changed