tracing: Initialize ret in syscall_enter_define_fields()

If syscall_enter_define_fields() is called on a system call with no
arguments, the return code variable "ret" will never get initialized.
Initialize it to zero.

Fixes: 04ae87a ("ftrace: Rework event_create_dir()")
Reported-by: Qian Cai <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: rostedt

kernel/trace/trace_syscalls.c

@@ -274,7 +274,8 @@ static int __init syscall_enter_define_fields(struct trace_event_call *call)
 	struct syscall_trace_enter trace;
 	struct syscall_metadata *meta = call->data;
 	int offset = offsetof(typeof(trace), args);
-	int ret, i;
+	int ret = 0;
+	int i;
 
 	for (i = 0; i < meta->nb_args; i++) {
 		ret = trace_define_field(call, meta->types[i],