lttng wrapper: add missing include to kallsyms wrapper

Needed to keep bissectability.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/lttng/wrapper/kallsyms.h

 #ifndef _LTT_WRAPPER_KALLSYMS_H
 #define _LTT_WRAPPER_KALLSYMS_H
 
+#include <linux/kallsyms.h>
+
 /*
  * Copyright (C) 2011 Avik Sil (avik.sil@linaro.org)
  *