xfs: fix rst syntax error in admin guide

Tables are supposed to have a matching line of "===" to signal the end
of a table.  The rst compiler gets grouchy if it encounters EOF instead,
so fix this warning.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
diff --git a/Documentation/admin-guide/xfs.rst b/Documentation/admin-guide/xfs.rst
index d2064a5..6178153 100644
--- a/Documentation/admin-guide/xfs.rst
+++ b/Documentation/admin-guide/xfs.rst
@@ -536,3 +536,4 @@
   cpumask        CPUs upon which the threads are allowed to run.
   nice           Relative priority of scheduling the threads.  These are the
                  same nice levels that can be applied to userspace processes.
+============     ===========