perf tools: Remove poll.h and wait.h from util.h

Not needed in this header, added to the places that need poll(), wait()
and a few other prototypes.

Link: http://lkml.kernel.org/n/tip-i39c7b6xmo1vwd9wxp6fmkl0@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-stat.c

@@ -78,6 +78,7 @@
 #include <math.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 #include <unistd.h>
 
 #include "sane_ctype.h"