kprobes: enable clean usage of get_kprobe

Allow clean use of get_kprobe() outside of core kprobe code. Ftrace makes use
of get_kprobe to identify probes installed on mcount call-sites.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: jkenisto@us.ibm.com
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/kprobes.h

@@ -259,6 +259,10 @@ void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head);
 struct jprobe;
 struct kretprobe;
 
+static inline struct kprobe *get_kprobe(void *addr)
+{
+	return NULL;
+}
 static inline struct kprobe *kprobe_running(void)
 {
 	return NULL;