documentation: Fix memory-barriers.txt section references

This commit fixes a couple of "Compiler Barrier" section references to
be "COMPILER BARRIER".  This makes it easier to find the section in
the usual text editors.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2016-01-06 14:23:03 -08:00
commit 895f554222