drm/syncobj: Fix compilation following partial revert

We need to include the revert of commit 783195ec ("drm/syncobj:
disable the timeline UAPI for now v2") along with undoing the change to
drm/i915.

Fixes: 131280a1 ("drm: Revert syncobj timeline changes.")
Cc: Christian König <christian.koenig@amd.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Chunming Zhou <david1.zhou@amd.com>
Cc: Eric Anholt <eric@anholt.net>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20181112152130.12275-1-chris@chris-wilson.co.uk