Make cacheflush(3) and get_fpc_csr(3) manual pages available on octeon.

OK deraadt@

src/etc/mtree/4.4BSD.dist

@@ -1,4 +1,4 @@
-#	$OpenBSD: 4.4BSD.dist,v 1.299 2017/08/21 20:52:06 rpe Exp $
+#	$OpenBSD: 4.4BSD.dist,v 1.300 2017/10/08 15:14:17 visa Exp $
 
 /set type=dir uname=root gname=wheel mode=0755
 
@@ -475,6 +475,8 @@ usr
             man3
                 loongson
                 ..
+                octeon
+                ..
                 sgi
                 ..
             ..