checkpatch: Remove ACCESS_ONCE() warning

Now that ACCESS_ONCE() has been excised from the kernel, any uses will
result in a build error, and we no longer need to whine about it in
checkpatch.

This patch removes the newly redundant warning.

Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@redhat.com
Link: http://lkml.kernel.org/r/20171127103824.36526-5-mark.rutland@arm.com


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