tracing, x86: remove duplicated #include

Remove duplicated #include in arch/x86/kernel/ftrace.c.
Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
LKML-Reference: <1238503291-2532-1-git-send-email-weiyi.huang@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/ftrace.c

@@ -20,7 +20,6 @@
 
 #include <asm/cacheflush.h>
 #include <asm/ftrace.h>
-#include <linux/ftrace.h>
 #include <asm/nops.h>
 #include <asm/nmi.h>