Remove explicit section reference in priv spec

Author: aswaterman

src/machine.adoc

@@ -2829,7 +2829,9 @@ and I/O regions may be accessed with either _relaxed_ or _strong_
 ordering. Accesses to an I/O region with relaxed ordering are generally
 observed by other harts and bus mastering devices in a manner similar to
 the ordering of accesses to an RVWMO memory region, as discussed in
-Section A.4.2 in Volume I of this specification. By contrast, accesses
+the I/O Ordering section in the RVWMO Explanatory Material appendix
+of Volume I of this specification.
+By contrast, accesses
 to an I/O region with strong ordering are generally observed by other
 harts and bus mastering devices in program order.