perf stat: Output running time and run/enabled ratio in CSV mode

perf stat: Output running time and run/enabled ratio in CSV mode

The information how much a counter ran in 'perf stat' can be quite
interesting for other tools to judge how trustworthy a measurement is.

Currently it is only output in non CSV mode.

This patches make perf stat always output the running time and the
enabled/running ratio in CSV mode.

This adds two new fields at the end for each line. I assume that
existing tools ignore new fields at the end, so it's on by default.

Only CSV mode is affected, no difference otherwise.

v2: Add extra print_running function
v3: Avoid printing nan
v4: Remove some elses and add brackets.
v5: Move non CSV case into print_running

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1426083387-17006-1-git-send-email-andi@firstfloor.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>