kobject: convert main fs kobject to use kobject_create

This also renames fs_subsys to fs_kobj to catch all current users with a
build error instead of a build warning which can easily be missed.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --cc fs/ecryptfs/main.c
Simple merge

diff --cc fs/fuse/inode.c
Simple merge

diff --cc fs/gfs2/sys.c
Simple merge

diff --cc fs/namespace.c
Simple merge

diff --cc include/linux/fs.h
Simple merge