There is a list_del corruption when remove the jffs2 module:

  list_del corruption, ffffffffa0623e60->next is NULL
  WARNING: CPU: 6 PID: 6332 at lib/list_debug.c:49 __list_del_entry_valid+0x98/0x130
  Modules linked in: jffs2(-) ]
  CPU: 6 PID: 6332 Comm: rmmod Tainted: G        W          6.1.0-rc2+ #5
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014
  RIP: 0010:__list_del_entry_valid+0x98/0x130
  ...
  Call Trace:
   <TASK>
   jffs2_unregister_compressor+0x3e/0xe0 [jffs2]
   jffs2_zlib_exit+0x11/0x30 [jffs2]
   jffs2_compressors_exit+0x1e/0x30 [jffs2]
   exit_jffs2_fs+0x16/0x44f [jffs2]
   __do_sys_delete_module.constprop.0+0x244/0x370
   do_syscall_64+0x35/0x80
   entry_SYSCALL_64_after_hwframe+0x46/0xb0

If one of the compressor initialize failed, the module always insert
success since jffs2_compressors_init() always return success, then
something bad may happen during remove the module.

For this scenario, let's insmod failed.
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>