NFS: Replace 16 seq_printf() calls by seq_puts()

Some strings should be put into a sequence.
Thus use the corresponding function “seq_puts”.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>