tracing: Make tracer_tracing_{off,on,is_on}() static

I have patches that will use tracer_tracing_on/off/is_on() in other
files, but as they are not ready to be merged yet, and Fengguang Wu's
sparse scripts pointed out that these functions were not declared
anywhere, I'll make them static for now.

When these functions are required to be used elsewhere, I'll remove
the static then.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -387,7 +387,7 @@ unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
 	TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD | TRACE_ITER_OVERWRITE |
 	TRACE_ITER_IRQ_INFO | TRACE_ITER_MARKERS | TRACE_ITER_FUNCTION;
 
-void tracer_tracing_on(struct trace_array *tr)
+static void tracer_tracing_on(struct trace_array *tr)
 {
 	if (tr->trace_buffer.buffer)
 		ring_buffer_record_on(tr->trace_buffer.buffer);
@@ -606,7 +606,7 @@ void tracing_snapshot_alloc(void)
 EXPORT_SYMBOL_GPL(tracing_snapshot_alloc);
 #endif /* CONFIG_TRACER_SNAPSHOT */
 
-void tracer_tracing_off(struct trace_array *tr)
+static void tracer_tracing_off(struct trace_array *tr)
 {
 	if (tr->trace_buffer.buffer)
 		ring_buffer_record_off(tr->trace_buffer.buffer);
@@ -649,7 +649,7 @@ void disable_trace_on_warning(void)
  *
  * Shows real state of the ring buffer if it is enabled or not.
  */
-int tracer_tracing_is_on(struct trace_array *tr)
+static int tracer_tracing_is_on(struct trace_array *tr)
 {
 	if (tr->trace_buffer.buffer)
 		return ring_buffer_record_is_on(tr->trace_buffer.buffer);