tracing: Convert tracer->enabled to counter

As tracers will soon be used by instances, the tracer enabled field
needs to be converted to a counter instead of a boolean.
This counter is protected by the trace_types_lock mutex.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -3916,7 +3916,7 @@ static void tracing_set_nop(struct trace_array *tr)
 	if (tr->current_trace == &nop_trace)
 		return;
 	
-	tr->current_trace->enabled = false;
+	tr->current_trace->enabled--;
 
 	if (tr->current_trace->reset)
 		tr->current_trace->reset(tr);
@@ -3962,7 +3962,7 @@ static int tracing_set_tracer(struct trace_array *tr, const char *buf)
 
 	trace_branch_disable();
 
-	tr->current_trace->enabled = false;
+	tr->current_trace->enabled--;
 
 	if (tr->current_trace->reset)
 		tr->current_trace->reset(tr);
@@ -4006,7 +4006,7 @@ static int tracing_set_tracer(struct trace_array *tr, const char *buf)
 	}
 
 	tr->current_trace = t;
-	tr->current_trace->enabled = true;
+	tr->current_trace->enabled++;
 	trace_branch_enable(tr);
  out:
 	mutex_unlock(&trace_types_lock);

kernel/trace/trace.h

@@ -362,8 +362,8 @@ struct tracer {
 						u32 mask, int set);
 	struct tracer		*next;
 	struct tracer_flags	*flags;
+	int			enabled;
 	bool			print_max;
-	bool			enabled;
 	bool			allow_instances;
 #ifdef CONFIG_TRACER_MAX_TRACE
 	bool			use_max_tr;