ftrace: split out hardirq ftrace code into own header

Impact: moving of function prototypes into own header file

ftrace.h is too big of a file for hardirq.h, and some archs will fail
to build because of the include dependencies not being met.

This patch pulls out the required prototypes for hardirq.h into a smaller
and safer ftrace_irq.h file.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/ftrace_irq.h b/include/linux/ftrace_irq.h
new file mode 100644
index 0000000..b1299d6
--- /dev/null
+++ b/include/linux/ftrace_irq.h
@@ -0,0 +1,13 @@
+#ifndef _LINUX_FTRACE_IRQ_H
+#define _LINUX_FTRACE_IRQ_H
+
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+extern void ftrace_nmi_enter(void);
+extern void ftrace_nmi_exit(void);
+#else
+static inline void ftrace_nmi_enter(void) { }
+static inline void ftrace_nmi_exit(void) { }
+#endif
+
+#endif /* _LINUX_FTRACE_IRQ_H */