perf session: Free cpu_map in perf_session__cpu_bitmap

This method uses a temporary struct cpu_map to figure out the cpus
present in the received cpu list in string form, but it failed to free
it after returning. Fix it.

Signed-off-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1390217980-22424-3-git-send-email-stfomichev@yandex-team.ru


[ Use goto + err = -1 to do the delete just once, in the normal exit path ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>