perf evlist: Simplify propagate_maps() logic

If evsel->cpus is to be reassigned then the current value must be "put",
which works even if it is NULL.  Simplify the current logic by moving
the "put" next to the assignment.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@intel.com>
Link: http://lkml.kernel.org/r/1441699142-18905-2-git-send-email-adrian.hunter@intel.com


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