tracing: Restore the const qualifier for field names and types definition

Restore the const qualifier in field's name and type parameters of
trace_define_field that was lost while solving a conflict.

Fields names and types are defined as builtin constant strings in
static TRACE_EVENTs. But kprobes allocates these dynamically.

That said, we still want to always pass these strings as const char *
in trace_define_fields() to avoid any further accidental writes on
the pointed strings.

Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_syscalls.c

@@ -193,8 +193,8 @@ int syscall_enter_define_fields(struct ftrace_event_call *call)
 		return ret;
 
 	for (i = 0; i < meta->nb_args; i++) {
-		ret = trace_define_field(call, (char *)meta->types[i],
-					 (char *)meta->args[i], offset,
+		ret = trace_define_field(call, meta->types[i],
+					 meta->args[i], offset,
 					 sizeof(unsigned long), 0,
 					 FILTER_OTHER);
 		offset += sizeof(unsigned long);