perf trace: Use the syscall raw_syscalls:sys_enter timestamp

perf trace: Use the syscall raw_syscalls:sys_enter timestamp

Instead of the one when another syscall takes place while another is being
processed (in another CPU, but we show it serialized, so need to "interrupt"
the other), and also when finally showing the sys_enter + sys_exit + duration,
where we were showing the sample->time for the sys_exit, duh.

Before:

  # perf trace sleep 1
  <SNIP>
     0.373 (   0.001 ms): close(fd: 3                   ) = 0
  1000.626 (1000.211 ms): nanosleep(rqtp: 0x7ffd6ddddfb0) = 0
  1000.653 (   0.003 ms): close(fd: 1                   ) = 0
  1000.657 (   0.002 ms): close(fd: 2                   ) = 0
  1000.667 (   0.000 ms): exit_group(                   )
  #

After:

  # perf trace sleep 1
  <SNIP>
     0.336 (   0.001 ms): close(fd: 3                   ) = 0
     0.373 (1000.086 ms): nanosleep(rqtp: 0x7ffe303e9550) = 0
  1000.481 (   0.002 ms): close(fd: 1                   ) = 0
  1000.485 (   0.001 ms): close(fd: 2                   ) = 0
  1000.494 (   0.000 ms): exit_group(                   )
[root@jouet linux]#

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-ecbzgmu2ni6glc6zkw8p1zmx@git.kernel.org
Fixes: 6138ea1fa1aa ("perf trace: Support interrupted syscalls")
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>