MAINTAINERS: Update cgroup entry

Fix wildcard patterns and add cgroup-v2 documentation.

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

MAINTAINERS

@@ -3906,9 +3906,10 @@ M:	Johannes Weiner <hannes@cmpxchg.org>
 L:	cgroups@vger.kernel.org
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git
 S:	Maintained
-F:	Documentation/cgroup*
+F:	Documentation/admin-guide/cgroup-v2.rst
+F:	Documentation/cgroup-v1/
 F:	include/linux/cgroup*
-F:	kernel/cgroup*
+F:	kernel/cgroup/
 
 CONTROL GROUP - CPUSET
 M:	Li Zefan <lizefan@huawei.com>