[PATCH] Use atomic64_set for 64-bit case of atomic_long_set

For some reason, the BITS_PER_LONG == 64 case of atomic_long_set
was using atomic_set instead of atomic64_set. This does not jive
with architectures which use an inline instead of a #define to
implement their atomic_set() primitives.

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>