tracing/events: add export symbols for trace events in modules

Impact: let modules add trace events

The trace event code requires some functions to be exported to allow
modules to use TRACE_EVENT. This patch adds EXPORT_SYMBOL_GPL to the
necessary functions.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 5c66aaf..8b9e621 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -53,6 +53,7 @@
 
 	return -ENOMEM;
 }
+EXPORT_SYMBOL_GPL(trace_define_field);
 
 static void ftrace_clear_events(void)
 {