perf tools: Remove string.h, unistd.h and sys/stat.h from util.h

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

Link: http://lkml.kernel.org/n/tip-xxtdsl6nsna82j7puwbdjqhs@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 07d87d2..8d724f0 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -16,6 +16,9 @@
 #include "util/hist.h"  /* perf_hist_config */
 #include "util/llvm-utils.h"   /* perf_llvm_config */
 #include "config.h"
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
 
 #include "sane_ctype.h"