tracing: Remove test of NULL define_fields callback

Every event (or event class) has it's define_fields callback,
so the test is redundant.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4BFA37BC.8080707@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index d3b4bdf..5bad9cb 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -987,23 +987,21 @@
 		 		  id);
 #endif
 
-	if (call->class->define_fields) {
-		/*
-		 * Other events may have the same class. Only update
-		 * the fields if they are not already defined.
-		 */
-		head = trace_get_fields(call);
-		if (list_empty(head)) {
-			ret = call->class->define_fields(call);
-			if (ret < 0) {
-				pr_warning("Could not initialize trace point"
-					   " events/%s\n", call->name);
-				return ret;
-			}
+	/*
+	 * Other events may have the same class. Only update
+	 * the fields if they are not already defined.
+	 */
+	head = trace_get_fields(call);
+	if (list_empty(head)) {
+		ret = call->class->define_fields(call);
+		if (ret < 0) {
+			pr_warning("Could not initialize trace point"
+				   " events/%s\n", call->name);
+			return ret;
 		}
-		trace_create_file("filter", 0644, call->dir, call,
-				  filter);
 	}
+	trace_create_file("filter", 0644, call->dir, call,
+			  filter);
 
 	trace_create_file("format", 0444, call->dir, call,
 			  format);