perf tools: Add arm64 triplets

Adds the triplet used for arm64 by Android. Others will want to add
their own later.

Signed-off-by: Elliott Hughes <enh@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20140814193920.A7D2D20572@enh.mtv.corp.google.com


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