libreboot-utils: improved randomness test

and the module bias handling is fully correct

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/libreboot-utils/include/common.h

@@ -391,7 +391,8 @@ void *rmalloc(size_t *size); /* don't ever use this */
 void rset(void *buf, size_t n);
 void *mkrbuf(size_t n);
 char *mkrstr(size_t n);
-int win_lottery(char **buf);
+int win_lottery(void);
+size_t rsize(void);
 
 /* Helper functions for command: dump
  */