kernel: Replace reference to ASSIGN_ONCE() with WRITE_ONCE() in comment

Looks like commit :

 43239cbe

 ("kernel: Change ASSIGN_ONCE(val, x) to WRITE_ONCE(x, val)")

left behind a reference to ASSIGN_ONCE(). Update this to WRITE_ONCE().

Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: borntraeger@de.ibm.com
Cc: dave@stgolabs.net
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/20150430115721.22278.94082.stgit@preeti.in.ibm.com


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