cgroup: fix cgroup_css() invocation in css_from_id()

ca8bdca ("cgroup: make cgroup_css() take cgroup_subsys * instead
and allow NULL subsys") missed one conversion in css_from_id(), which
was newly added.  As css_from_id() doesn't have any user yet, this
doesn't break anything other than generating a build warning.

Convert it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: kbuild test robot <fengguang.wu@intel.com>

kernel/cgroup.c

@@ -5729,7 +5729,7 @@ struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
 
 	cgrp = idr_find(&ss->root->cgroup_idr, id);
 	if (cgrp)
-		return cgroup_css(cgrp, ss->subsys_id);
+		return cgroup_css(cgrp, ss);
 	return NULL;
 }