perf data: Switch to multiple cpu stream files

Currently we store the data into single data strea/file. The cpu if data
is stored within the event sample. The lttng puts the CPU number that
belongs to the event into the packet context instead into the event.

This patch makes sure that the trace produce by perf does look the same
way. We now use one stream per-CPU. Having it all in one stream
increased the total size of the resulting file. The test went from
416KiB (with perf_cpu event member) to 24MiB due to the required (and
pointless) flush. With the per-cpu streams the total size went up to
588KiB.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jeremie Galarneau <jgalar@efficios.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1429372220-6406-3-git-send-email-jolsa@kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>