perf color: Add missing stdarg.g to color.h

It was getting the va_list definition by luck.

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-4mavb7pgt2nw9lsew1xuez09@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/color.h

@@ -3,6 +3,7 @@
 #define __PERF_COLOR_H
 
 #include <stdio.h>
+#include <stdarg.h>
 
 /* "\033[1;38;5;2xx;48;5;2xxm\0" is 23 bytes */
 #define COLOR_MAXLEN 24