Add support for 'perf kvm stat' on arm64 platform.

Example:

  # perf kvm stat report

Analyze events for all VMs, all VCPUs:

    VM-EXIT    Samples  Samples%     Time%    Min Time    Max Time         Avg time

   DABT_LOW     661867    98.91%    40.45%      2.19us   3364.65us      6.24us ( +-   0.34% )
        IRQ       4598     0.69%    57.44%      2.89us   3397.59us   1276.27us ( +-   1.61% )
        WFx       1475     0.22%     1.71%      2.22us   3388.63us    118.31us ( +-   8.69% )
   IABT_LOW       1018     0.15%     0.38%      2.22us   2742.07us     38.29us ( +-  12.55% )
      SYS64        180     0.03%     0.01%      2.07us    112.91us      6.57us ( +-  14.95% )
      HVC64         17     0.00%     0.01%      2.19us    322.35us     42.95us ( +-  58.98% )

Total Samples:669155, Total events handled time:10216387.86us.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Tested-by: Leo Yan <leo.yan@linaro.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Suleiman Souhlal <suleiman@google.com>
Link: http://lore.kernel.org/lkml/20201027062421.463355-1-sergey.senozhatsky@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>