drm/i915/gt: Defer engine registration until fully initialised

Only add the engine to the available set of uabi engines once it has
been fully initialised and we know we want it in the public set.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michał Wajdeczko <michal.wajdeczko@intel.com>
Cc: Andi Shyti <andi.shyti@intel.com>
Acked-by: Andi Shyti <andi.shyti@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191107081252.10542-17-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_engine_cs.c

@@ -344,7 +344,6 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id)
 	gt->engine_class[info->class][info->instance] = engine;
 	gt->engine[id] = engine;
 
-	intel_engine_add_user(engine);
 	gt->i915->engine[id] = engine;
 
 	return 0;
@@ -481,6 +480,8 @@ int intel_engines_init(struct intel_gt *gt)
 		err = init(engine);
 		if (err)
 			goto cleanup;
+
+		intel_engine_add_user(engine);
 	}
 
 	return 0;