tools/memory-model: Remove ACCESS_ONCE() from model

Since commit:

  b899a850 ("compiler.h: Remove ACCESS_ONCE()")

... there has been no definition of ACCESS_ONCE() in the kernel tree,
and it has been necessary to use READ_ONCE() or WRITE_ONCE() instead.

Correspondingly, let's remove ACCESS_ONCE() from the kernel memory
model.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/20180716180605.16115-6-paulmck@linux.vnet.ibm.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>