ext2: Drop fragment support

stable inclusion
from stable-v5.10.190
commit d328849fb63bfce7695245b932bc5f295bea5eb6
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I928UI

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d328849fb63bfce7695245b932bc5f295bea5eb6



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commit 404615d7 upstream.

Ext2 has fields in superblock reserved for subblock allocation support.
However that never landed. Drop the many years dead code.

Reported-by:  <syzbot+af5e10f73dbff48f70af@syzkaller.appspotmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>