perf tools: Fix AAAAARGH64 memory barriers

Someone got the load and store barriers mixed up for AAAAARGH64.  Turn
them the right side up.

Reported-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Fixes: a94d342b ("tools/perf: Add required memory barriers")
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20140124154002.GF31570@twins.programming.kicks-ass.net


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>