nfsd: remove unused parameter of nfsd_file_mark_find_or_create

Commit 427f5f83 ("NFSD: Ensure nf_inode is never dereferenced") passes
inode directly to nfsd_file_mark_find_or_create instead of getting it from
nf, so there is no need to pass nf.

Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>