MAINTAINERS: add memfd, shmem quota files to shmem section

These files seem best suited to shmem.

Link: https://lkml.kernel.org/r/20250617161359.166955-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: ljskernel

MAINTAINERS

@@ -15740,7 +15740,6 @@ F:	Documentation/admin-guide/mm/
 F:	Documentation/mm/
 F:	include/linux/gfp.h
 F:	include/linux/gfp_types.h
-F:	include/linux/memfd.h
 F:	include/linux/memory_hotplug.h
 F:	include/linux/memory-tiers.h
 F:	include/linux/mempolicy.h
@@ -25042,8 +25041,11 @@ M:	Hugh Dickins <hughd@google.com>
 R:	Baolin Wang <baolin.wang@linux.alibaba.com>
 L:	linux-mm@kvack.org
 S:	Maintained
+F:	include/linux/memfd.h
 F:	include/linux/shmem_fs.h
+F:	mm/memfd.c
 F:	mm/shmem.c
+F:	mm/shmem_quota.c
 
 TOMOYO SECURITY MODULE
 M:	Kentaro Takeda <takedakn@nttdata.co.jp>