testcases/kernel/syscalls: clean up old style prototypes

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/testcases/kernel/syscalls/kill/kill08.c b/testcases/kernel/syscalls/kill/kill08.c
index a525606..1c2a9f7 100644
--- a/testcases/kernel/syscalls/kill/kill08.c
+++ b/testcases/kernel/syscalls/kill/kill08.c
@@ -159,7 +159,7 @@
 /*
  * do_child()
  */
-void do_child()
+void do_child(void)
 {
 	int exno = 1;