When insmod ubifs.ko, a kmemleak reported as below:

 unreferenced object 0xffff88817fb1a780 (size 8):
   comm "insmod", pid 25265, jiffies 4295239702 (age 100.130s)
   hex dump (first 8 bytes):
     75 62 69 66 73 00 ff ff                          ubifs...
   backtrace:
     [<ffffffff81b3fc4c>] slab_post_alloc_hook+0x9c/0x3c0
     [<ffffffff81b44bf3>] __kmalloc_track_caller+0x183/0x410
     [<ffffffff8198d3da>] kstrdup+0x3a/0x80
     [<ffffffff8198d486>] kstrdup_const+0x66/0x80
     [<ffffffff83989325>] kvasprintf_const+0x155/0x190
     [<ffffffff83bf55bb>] kobject_set_name_vargs+0x5b/0x150
     [<ffffffff83bf576b>] kobject_set_name+0xbb/0xf0
     [<ffffffff8100204c>] do_one_initcall+0x14c/0x5a0
     [<ffffffff8157e380>] do_init_module+0x1f0/0x660
     [<ffffffff815857be>] load_module+0x6d7e/0x7590
     [<ffffffff8158644f>] __do_sys_finit_module+0x19f/0x230
     [<ffffffff815866b3>] __x64_sys_finit_module+0x73/0xb0
     [<ffffffff88c98e85>] do_syscall_64+0x35/0x80
     [<ffffffff88e00087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

When kset_register() failed, we should call kset_put to cleanup it.

Fixes: 2e3cbf42 ("ubifs: Export filesystem error counters")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>