tools/memory-order: Update the cheat-sheet to show that smp_mb__after_atomic() orders later RMW operations

The current cheat sheet does not claim that smp_mb__after_atomic()
orders later RMW atomic operations, which it must, at least against
earlier RMW atomic operations and whatever precedes them.

This commit therefore adds the needed "Y".

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-6-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

tools/memory-model/Documentation/cheatsheet.txt

@@ -14,7 +14,7 @@ smp_wmb()                                  Y    W           Y       Y    W
 smp_mb() & synchronize_rcu()  CP        Y  Y    Y        Y  Y   Y   Y    Y
 Successful full non-void RMW  CP     Y  Y  Y    Y     Y  Y  Y   Y   Y    Y   Y
 smp_mb__before_atomic()       CP        Y  Y    Y        a  a   a   a    Y
-smp_mb__after_atomic()        CP        a  a    Y        Y  Y   Y   Y
+smp_mb__after_atomic()        CP        a  a    Y        Y  Y   Y   Y    Y
 
 
 Key:	C:	Ordering is cumulative