Make devctl_queue_data_f and devctl_queue_data private.

I thought we'd need them, but nobody is using them. Narrow the interface. This
will facilitate changes in the future.

sys/kern/subr_bus.c

@@ -607,7 +607,7 @@ devctl_process_running(void)
  * assumed that @p data is properly formatted.  It is further assumed
  * that @p data is allocated using the M_BUS malloc type.
  */
-void
+static void
 devctl_queue_data_f(char *data, int flags)
 {
 	struct dev_event_info *n1 = NULL, *n2 = NULL;
@@ -653,7 +653,7 @@ devctl_queue_data_f(char *data, int flags)
 	return;
 }
 
-void
+static void
 devctl_queue_data(char *data)
 {
 	devctl_queue_data_f(data, M_NOWAIT);

sys/sys/bus.h

@@ -156,16 +156,13 @@ struct devreq {
 
 /**
  * devctl hooks.  Typically one should use the devctl_notify
- * hook to send the message.  However, devctl_queue_data is also
- * included in case devctl_notify isn't sufficiently general.
+ * hook to send the message.
  */
 boolean_t devctl_process_running(void);
 void devctl_notify_f(const char *__system, const char *__subsystem,
     const char *__type, const char *__data, int __flags);
 void devctl_notify(const char *__system, const char *__subsystem,
     const char *__type, const char *__data);
-void devctl_queue_data_f(char *__data, int __flags);
-void devctl_queue_data(char *__data);
 struct sbuf;
 void devctl_safe_quote_sb(struct sbuf *__sb, const char *__src);