tracing: Add helper function tracing_is_disabled()

This patch creates the function 'tracing_is_disabled', which
can be used outside of trace.c.

Link: http://lkml.kernel.org/r/1382141754-12155-1-git-send-email-geyslan@gmail.com

Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 9c27cda..4388e16 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -514,6 +514,7 @@
 void tracing_reset_current(int cpu);
 void tracing_reset_all_online_cpus(void);
 int tracing_open_generic(struct inode *inode, struct file *filp);
+bool tracing_is_disabled(void);
 struct dentry *trace_create_file(const char *name,
 				 umode_t mode,
 				 struct dentry *parent,