nfsd: use DEFINE_SHOW_ATTRIBUTE to define client_info_fops

[ Upstream commit 1d7f6b30 ]

Use DEFINE_SHOW_ATTRIBUTE helper macro to simplify the code.

inode is converted from seq_file->file instead of seq_file->private in
client_info_show().

Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>