If jffs2_iget() or d_make_root() in jffs2_do_fill_super() returns
an error, we can observe the following kmemleak report:

--------------------------------------------
unreferenced object 0xffff888105a65340 (size 64):
  comm "mount", pid 710, jiffies 4302851558 (age 58.239s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff859c45e5>] kmem_cache_alloc_trace+0x475/0x8a0
    [<ffffffff86160146>] jffs2_sum_init+0x96/0x1a0
    [<ffffffff86140e25>] jffs2_do_mount_fs+0x745/0x2120
    [<ffffffff86149fec>] jffs2_do_fill_super+0x35c/0x810
    [<ffffffff8614aae9>] jffs2_fill_super+0x2b9/0x3b0
    [...]
unreferenced object 0xffff8881bd7f0000 (size 65536):
  comm "mount", pid 710, jiffies 4302851558 (age 58.239s)
  hex dump (first 32 bytes):
    bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
    bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
  backtrace:
    [<ffffffff858579ba>] kmalloc_order+0xda/0x110
    [<ffffffff85857a11>] kmalloc_order_trace+0x21/0x130
    [<ffffffff859c2ed1>] __kmalloc+0x711/0x8a0
    [<ffffffff86160189>] jffs2_sum_init+0xd9/0x1a0
    [<ffffffff86140e25>] jffs2_do_mount_fs+0x745/0x2120
    [<ffffffff86149fec>] jffs2_do_fill_super+0x35c/0x810
    [<ffffffff8614aae9>] jffs2_fill_super+0x2b9/0x3b0
    [...]
--------------------------------------------

This is because the resources allocated in jffs2_sum_init() are not
released. Call jffs2_sum_exit() to release these resources to solve
the problem.

Fixes: e631ddba ("[JFFS2] Add erase block summary support (mount time improvement)")
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>