On aarch64 CPU related events are not under event_source/devices/cpu/events,
they're under event_source/devices/armv8_pmuv3_0/events on my machine.
Using current auto-complete script will generate below error:

  [root@localhost bin]# perf stat -e
  ls: cannot access '/sys/bus/event_source/devices/cpu/events': No such file or directory

Fix this by not testing /sys/bus/event_source/devices/cpu/events on
aarch64 machine.

Fixes: 74cd5815 ("perf tool: Improve bash command line auto-complete for multiple events with comma")
Reviewed-by: James Clark <james.clark@arm.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linuxarm@huawei.com
Cc: prime.zeng@hisilicon.com
Link: https://lore.kernel.org/r/20230207035057.43394-1-yangyicong@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>