locking/lockref: Remove homebrew cmpxchg64_relaxed() macro definition

cmpxchg64_relaxed() is now defined by linux/atomic.h, so we can
remove our local definition from the lockref code.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NPeter 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/1438880084-18856-5-git-send-email-will.deacon@arm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

lib/lockref.c

@@ -3,14 +3,6 @@
 
 #if USE_CMPXCHG_LOCKREF
 
-/*
- * Allow weakly-ordered memory architectures to provide barrier-less
- * cmpxchg semantics for lockref updates.
- */
-#ifndef cmpxchg64_relaxed
-# define cmpxchg64_relaxed cmpxchg64
-#endif
-
 /*
  * Note that the "cmpxchg()" reloads the "old" value for the
  * failure case.