Convert the tracepoint.py file to python3 as many of the files in
tools/perf are already written in python3.

Committer testing:

  # export PYTHONPATH=/tmp/build/perf/python/
  # python3 ~acme/git/perf/tools/perf/python/tracepoint.py | head
  time 67394457376909 prev_comm=swapper/12 prev_pid=0 prev_prio=120 prev_state=0x0 ==> next_comm=gnome-terminal- next_pid=3313 next_prio=120
  time 67394457807669 prev_comm=python3 prev_pid=1485930 prev_prio=120 prev_state=0x1 ==> next_comm=swapper/13 next_pid=0 next_prio=120
  time 67394457811859 prev_comm=swapper/13 prev_pid=0 prev_prio=120 prev_state=0x0 ==> next_comm=python3 next_pid=1485930 next_prio=120
  time 67394457824929 prev_comm=python3 prev_pid=1485930 prev_prio=120 prev_state=0x1 ==> next_comm=swapper/13 next_pid=0 next_prio=120
  time 67394457831899 prev_comm=swapper/13 prev_pid=0 prev_prio=120 prev_state=0x0 ==> next_comm=python3 next_pid=1485930 next_prio=120
  time 67394457842299 prev_comm=python3 prev_pid=1485930 prev_prio=120 prev_state=0x1 ==> next_comm=swapper/13 next_pid=0 next_prio=120
  time 67394457844179 prev_comm=swapper/13 prev_pid=0 prev_prio=120 prev_state=0x0 ==> next_comm=python3 next_pid=1485930 next_prio=120
  time 67394457853879 prev_comm=python3 prev_pid=1485930 prev_prio=120 prev_state=0x1 ==> next_comm=swapper/13 next_pid=0 next_prio=120
  time 67394457856339 prev_comm=swapper/13 prev_pid=0 prev_prio=120 prev_state=0x0 ==> next_comm=python3 next_pid=1485930 next_prio=120
  time 67394457865659 prev_comm=python3 prev_pid=1485930 prev_prio=120 prev_state=0x1 ==> next_comm=swapper/13 next_pid=0 next_prio=120
  Traceback (most recent call last):
    File "/var/home/acme/git/perf/tools/perf/python/tracepoint.py", line 48, in <module>
      main()
    File "/var/home/acme/git/perf/tools/perf/python/tracepoint.py", line 37, in main
      print("time %u prev_comm=%s prev_pid=%d prev_prio=%d prev_state=0x%x ==> next_comm=%s next_pid=%d next_prio=%d" % (
  BrokenPipeError: [Errno 32] Broken pipe
  #
Signed-off-by: Tanu M <tanu235m@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/linux-perf-users/CAPS78prawYzRZnyhWjgOnGw4EwoswNwztvfZFdCOPOydFzVwzQ@mail.gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>