ftrace: Return ENOTSUPP when DYNAMIC_FTRACE_WITH_DIRECT_CALLS is not configured

When CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS is not set it's best to
have the stub functions return ENOTSUPP instead of ENODEV,
otherwise ENODEV is a valid error when ip is incorrect which is
indistinguishable from ftrace not compiled in.

Link: http://lkml.kernel.org/r/CAADnVQ+OzTikM9EhrfsC7NFsVYhATW1SVHxK64w3xn9qpk81pg@mail.gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

include/linux/ftrace.h

@@ -268,16 +268,16 @@ int ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
 # define ftrace_direct_func_count 0
 static inline int register_ftrace_direct(unsigned long ip, unsigned long addr)
 {
-	return -ENODEV;
+	return -ENOTSUPP;
 }
 static inline int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
 {
-	return -ENODEV;
+	return -ENOTSUPP;
 }
 static inline int modify_ftrace_direct(unsigned long ip,
 				       unsigned long old_addr, unsigned long new_addr)
 {
-	return -ENODEV;
+	return -ENOTSUPP;
 }
 static inline struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr)
 {