drm/i915: Adding missing '; ' to ENGINE_INSTANCES

Tvrtko spotted that I left off the trailing ';'. It went unnoticed by CI
because despite adding the macro, we didn't add a user, so include one as
well (a simple debug print).

Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 97ee6e92

 ("drm/i915: stop storing the media fuse")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190326180007.11722-1-chris@chris-wilson.co.uk