MAINTAINERS: add kernfs entry

My kernfs patch slipped through because I didn't know which maintainer
to CC. Have been told it's gkh. Add an entry, and sort the file patterns
while we are here.
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -3333,16 +3333,17 @@ F:	drivers/block/drbd/
 F:	lib/lru_cache.c
 F:	Documentation/blockdev/drbd/
 
-DRIVER CORE, KOBJECTS, DEBUGFS AND SYSFS
+DRIVER CORE, KOBJECTS, DEBUGFS, KERNFS AND SYSFS
 M:	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
 S:	Supported
 F:	Documentation/kobject.txt
 F:	drivers/base/
-F:	fs/sysfs/
 F:	fs/debugfs/
-F:	include/linux/kobj*
+F:	fs/kernfs/
+F:	fs/sysfs/
 F:	include/linux/debugfs.h
+F:	include/linux/kobj*
 F:	lib/kobj*
 
 DRM DRIVERS