ubifs: fix unencrypted journal write

Without this, I get the following on reboot:

UBIFS error (ubi1:0 pid 703): ubifs_load_znode: bad target node (type 1) length (8240)
UBIFS error (ubi1:0 pid 703): ubifs_load_znode: have to be in range of 48-4144
UBIFS error (ubi1:0 pid 703): ubifs_load_znode: bad indexing node at LEB 13:11080, error 5
 magic          0x6101831
 crc            0xb1cb246f
 node_type      9 (indexing node)
 group_type     0 (no node group)
 sqnum          546
 len            128
 child_cnt      5
 level          0
 Branches:
 0: LEB 14:72088 len 161 key (133, inode)
 1: LEB 14:81120 len 160 key (134, inode)
 2: LEB 20:26624 len 8240 key (134, data, 0)
 3: LEB 14:81280 len 160 key (135, inode)
 4: LEB 20:34864 len 8240 key (135, data, 0)
UBIFS warning (ubi1:0 pid 703): ubifs_ro_mode.part.0: switched to read-only mode, error -22
CPU: 0 PID: 703 Comm: mount Not tainted 4.9.0-next-20161213+ #1197
Hardware name: Atmel SAMA5
[<c010d2ac>] (unwind_backtrace) from [<c010b250>] (show_stack+0x10/0x14)
[<c010b250>] (show_stack) from [<c024df94>] (ubifs_jnl_update+0x2e8/0x614)
[<c024df94>] (ubifs_jnl_update) from [<c0254bf8>] (ubifs_mkdir+0x160/0x204)
[<c0254bf8>] (ubifs_mkdir) from [<c01a6030>] (vfs_mkdir+0xb0/0x104)
[<c01a6030>] (vfs_mkdir) from [<c0286070>] (ovl_create_real+0x118/0x248)
[<c0286070>] (ovl_create_real) from [<c0283ed4>] (ovl_fill_super+0x994/0xaf4)
[<c0283ed4>] (ovl_fill_super) from [<c019c394>] (mount_nodev+0x44/0x9c)
[<c019c394>] (mount_nodev) from [<c019c4ac>] (mount_fs+0x14/0xa4)
[<c019c4ac>] (mount_fs) from [<c01b5338>] (vfs_kern_mount+0x4c/0xd4)
[<c01b5338>] (vfs_kern_mount) from [<c01b6b80>] (do_mount+0x154/0xac8)
[<c01b6b80>] (do_mount) from [<c01b782c>] (SyS_mount+0x74/0x9c)
[<c01b782c>] (SyS_mount) from [<c0107f80>] (ret_fast_syscall+0x0/0x3c)
UBIFS error (ubi1:0 pid 703): ubifs_mkdir: cannot create directory, error -22
overlayfs: failed to create directory /mnt/ovl/work/work (errno: 22); mounting read-only

Fixes: 7799953b34d1 ("ubifs: Implement encrypt/decrypt for all IO")
Signed-off-by: Peter Rosin <peda@axentia.se>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Richard Weinberger <richard@nod.at>