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

It was getting the va_list definition by luck.

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/color.h

···
 #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