drm/i915/selftests: Drop stale timeline constructor assert

Since we pass around encoded parameters to the kernel context
constructor using the ce->timeline pointer, we can no longer assert that
it should be zero for mock timeline construction.

Fixes: d1bf5dd ("drm/i915/gt: Support multiple pinned timelines")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200731102206.6793-1-chris@chris-wilson.co.uk
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
[Joonas: Updated Fixes: link after rebasing and reordering into drm-intel-gt-next branch]
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

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

@@ -152,7 +152,6 @@ static int mock_context_alloc(struct intel_context *ce)
 	if (!ce->ring)
 		return -ENOMEM;
 
-	GEM_BUG_ON(ce->timeline);
 	ce->timeline = intel_timeline_create(ce->engine->gt);
 	if (IS_ERR(ce->timeline)) {
 		kfree(ce->engine);