NFS: out of date comment regarding O_EXCL above nfs3_proc_create()

Hi Trond,

Recently we were observing the behaviour difference between a 2.4.x and
2.6.x kernel with respect to O_EXCL. A comment from 2.4.x era, "For now,
we don't implement O_EXCL." seems inaccurate in TOT.

If so, here's a patch to remove the comment.

This patch is against:
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6



Signed-off-by: Harshula Jayasuriya <harshula@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>