NFS: Fix a problem with the legacy binary mount code

Apparently, am-utils is still using the legacy binary mountdata interface,
and is having trouble parsing /proc/mounts due to the 'port=' field being
incorrectly set.

The following patch should fix up the regression.

Reported-by: Marius Tolzmann <tolzmann@molgen.mpg.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org