doc: Update control-dependencies section of memory-barriers.txt
In the following example, if MAX is defined to be 1, then the compiler
knows (Q % MAX) is equal to zero. The compiler can therefore throw
away the "then" branch (and the "if"), retaining only the "else" branch.
Signed-off-by: pierre Kuo <vichy.kuo@gmail.com> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>