selftests/futex: Add stdio used for logging

Fix missing printf compile warnings.

Signed-off-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/futex/include/logging.h

@@ -21,6 +21,7 @@
 #ifndef _LOGGING_H
 #define _LOGGING_H
 
+#include <stdio.h>
 #include <string.h>
 #include <unistd.h>
 #include <linux/futex.h>