locking, include/llist: Use linux/atomic.h instead of asm/cmpxchg.h

locking, include/llist: Use linux/atomic.h instead of asm/cmpxchg.h

Including an asm/ header directly is best avoided, so use linux/atomic.h
instead of asm/cmpxchg.h in linux/llist.h.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman.Long@hp.com
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1438880084-18856-8-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>