atomic: fix a typo in atomic_long_xchg()

atomic_long_xchg() is not correctly defined for 32bit arches.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-generic/atomic.h

@@ -251,7 +251,7 @@ static inline long atomic_long_add_unless(atomic_long_t *l, long a, long u)
 #define atomic_long_cmpxchg(l, old, new) \
 	(atomic_cmpxchg((atomic_t *)(l), (old), (new)))
 #define atomic_long_xchg(v, new) \
-	(atomic_xchg((atomic_t *)(l), (new)))
+	(atomic_xchg((atomic_t *)(v), (new)))
 
 #endif  /*  BITS_PER_LONG == 64  */