nfsd: fix file memleak on client_opens_release

stable inclusion
from stable-v6.6.3
commit 47a9c946d850671c2492bb0cc20f151a3648a6de
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8LBQP

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=47a9c946d850671c2492bb0cc20f151a3648a6de



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commit bc1b5acb40201a0746d68a7d7cfc141899937f4f upstream.

seq_release should be called to free the allocated seq_file

Cc: stable@vger.kernel.org # v5.3+
Signed-off-by: Mahmoud Adam <mngyadam@amazon.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Fixes: 78599c42 ("nfsd4: add file to display list of client's opens")
Reviewed-by: NeilBrown <neilb@suse.de>
Tested-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>