tracing: use proper export symbol for tracing api

When adding the EXPORT_SYMBOL to some of the tracing API, I accidently
used EXPORT_SYMBOL instead of EXPORT_SYMBOL_GPL. This patch fixes
that mistake.

[ Impact: export the tracing code only for GPL modules ]

Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -887,21 +887,21 @@ trace_current_buffer_lock_reserve(int type, unsigned long len,
 	return trace_buffer_lock_reserve(&global_trace,
 					 type, len, flags, pc);
 }
-EXPORT_SYMBOL(trace_current_buffer_lock_reserve);
+EXPORT_SYMBOL_GPL(trace_current_buffer_lock_reserve);
 
 void trace_current_buffer_unlock_commit(struct ring_buffer_event *event,
 					unsigned long flags, int pc)
 {
 	__trace_buffer_unlock_commit(&global_trace, event, flags, pc, 1);
 }
-EXPORT_SYMBOL(trace_current_buffer_unlock_commit);
+EXPORT_SYMBOL_GPL(trace_current_buffer_unlock_commit);
 
 void trace_nowake_buffer_unlock_commit(struct ring_buffer_event *event,
 					unsigned long flags, int pc)
 {
 	__trace_buffer_unlock_commit(&global_trace, event, flags, pc, 0);
 }
-EXPORT_SYMBOL(trace_nowake_buffer_unlock_commit);
+EXPORT_SYMBOL_GPL(trace_nowake_buffer_unlock_commit);
 
 void trace_current_buffer_discard_commit(struct ring_buffer_event *event)
 {