ftrace: Fix warning when CONFIG_FUNCTION_TRACER is not defined

commit 04da85b86188f224cc9b391b5bdd92a3ba20ffcf upstream.

The struct ftrace_hash was declared within CONFIG_FUNCTION_TRACER
but was referenced outside of it.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index ed0eb52..f0c0e8a 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -19,6 +19,8 @@
 
 #include <asm/ftrace.h>
 
+struct ftrace_hash;
+
 #ifdef CONFIG_FUNCTION_TRACER
 
 extern int ftrace_enabled;
@@ -29,8 +31,6 @@
 
 typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip);
 
-struct ftrace_hash;
-
 enum {
 	FTRACE_OPS_FL_ENABLED		= 1 << 0,
 	FTRACE_OPS_FL_GLOBAL		= 1 << 1,