Documentation/memory-barriers.txt: ACCESS_ONCE() provides cache coherence
Documentation/memory-barriers.txt: ACCESS_ONCE() provides cache coherence

The ACCESS_ONCE() primitive provides cache coherence, but the
documentation does not clearly state this.  This commit therefore upgrades
the documentation.

Signed-off-by: Paul E. McKenney <1e0ce936bb9b355d257bf5790d2513c3f28be22b@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <c028c213ed5efcf30c3f4fc7361dbde0c893c5b7@joshtriplett.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs