ftrace: fix include file dependency

Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

include/linux/ftrace.h

@@ -4,6 +4,7 @@
 #ifdef CONFIG_FTRACE
 
 #include <linux/linkage.h>
+#include <linux/fs.h>
 
 extern int ftrace_enabled;
 extern int