perf evsel: Add missing perf/evsel.h header in util/evsel.h

Since util/evsel.h uses perf_evsel__cpus() that has its prototype in
libperf's perf/evsel.h file, we need it explicitely included.

This was working by luck as util/evsel.h includes counts.h, but that is
not necessary, just some forward declarations, so, before we remove
counts.h from util/evsel.h, add what is realli needed.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-nfb9e0t4jm9zhvr0q86hc29d@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.h

@@ -8,6 +8,7 @@
 #include <linux/perf_event.h>
 #include <linux/types.h>
 #include <internal/evsel.h>
+#include <perf/evsel.h>
 #include "symbol_conf.h"
 #include "cpumap.h"
 #include "counts.h"