tracing/events: add support for modules to TRACE_EVENT

Impact: allow modules to add TRACE_EVENTS on load

This patch adds the final hooks to allow modules to use the TRACE_EVENT
macro. A notifier and a data structure are used to link the TRACE_EVENTs
defined in the module to connect them with the ftrace event tracing system.

It also adds the necessary automated clean ups to the trace events when a
module is removed.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 955b967..60c5323 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -477,6 +477,7 @@
 __attribute__((section("_ftrace_events"))) event_##call = {		\
 	.name			= #call,				\
 	.system			= __stringify(TRACE_SYSTEM),		\
+	.event			= &ftrace_event_type_##call,		\
 	.raw_init		= ftrace_raw_init_event_##call,		\
 	.regfunc		= ftrace_raw_reg_event_##call,		\
 	.unregfunc		= ftrace_raw_unreg_event_##call,	\