cifs: Fix memory leak on the deferred close

In the Linux kernel, the following vulnerability has been resolved:

cifs: Fix memory leak on the deferred close

xfstests on smb21 report kmemleak as below:

unreferenced object 0xffff8881767d6200 (size 64):

comm "xfs_io", pid 1284, jiffies 4294777434 (age 20.789s)

hex dump (first 32 bytes):

80 5a d0 11 81 88 ff ff 78 8a aa 63 81 88 ff ff .Z......x..c....

00 71 99 76 81 88 ff ff 00 00 00 00 00 00 00 00 .q.v............

backtrace:

[<00000000ad04e6ea>] cifs_close+0x92/0x2c0

[<0000000028b93c82>] __fput+0xff/0x3f0

[<00000000d8116851>] task_work_run+0x85/0xc0

[<0000000027e14f9e>] do_exit+0x5e5/0x1240

[<00000000fb492b95>] do_group_exit+0x58/0xe0

[<00000000129a32d9>] __x64_sys_exit_group+0x28/0x30

[<00000000e3f7d8e9>] do_syscall_64+0x35/0x80

[<00000000102e8a0b>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

When cancel the deferred close work, we should also cleanup the struct

cifs_deferred_close.