perf symbols: We need util.h in symbol-elf.c for zfree()

Continuing to untangle the headers, we're about to remove the old odd
baggage that is tools/perf/util/include/linux/ctype.h.

Cc: Adrian Hunter <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Link: https://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/symbol-elf.c

···
 #include "machine.h"
 #include "vdso.h"
 #include "debug.h"
+#include "util.h"
 #include "sane_ctype.h"
 #include <symbol/kallsyms.h>