perf target: Add cpu flag to sample_type if target has cpu

Add PERF_SAMPLE_CPU flag into attr->sample_type if an user specified any
of cpu target (either system-wide or cpu list).

It will show correct values when cpu sort key is given for perf top and
perf report.

Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1337564527-9367-1-git-send-email-namhyung.kim@lge.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>