tools/memory-model: Fix cheat sheet typo

"RWM" should be "RMW".
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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
Cc: stern@rowland.harvard.edu
Link: http://lkml.kernel.org/r/1526340837-12222-4-git-send-email-paulmck@linux.vnet.ibm.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

tools/memory-model/Documentation/cheatsheet.txt

                                   Prior Operation     Subsequent Operation
                                   ---------------  ---------------------------
-                               C  Self  R  W  RWM  Self  R  W  DR  DW  RMW  SV
+                               C  Self  R  W  RMW  Self  R  W  DR  DW  RMW  SV
                               --  ----  -  -  ---  ----  -  -  --  --  ---  --
 
 Store, e.g., WRITE_ONCE()            Y                                       Y