perf thread_map: Create dummy constructor out of open coded equivalent

Create a dummy thread_map, one that has just one entry and it is -1,
meaning 'all threads', as this ends up going down to perf_event_open().

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-8av26cz8uxmbnihl5mmrygp9@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>