perf evlist: Move destruction of maps to evlist destructor

Instead of requiring tools to do an extra destructor call just before
calling perf_evlist__delete.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
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-0jd2ptzyikxb5wp7inzz2ah2@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/mmap-basic.c

@@ -143,6 +143,8 @@ out_close_fd:
 		perf_evsel__close_fd(evsels[i], 1, threads->nr);
 out_free_evlist:
 	perf_evlist__delete(evlist);
+	cpus	= NULL;
+	threads = NULL;
 out_free_cpus:
 	cpu_map__delete(cpus);
 out_free_threads: