tracing: Remove access to trace_flags in trace_printk.c

In the effort to move the global trace_flags to the tracing instances, the
direct access to trace_flags must be removed from trace_printk.c

Instead, add a new trace_printk_enabled boolean that is set by a new access
function trace_printk_control(), that will enable or disable trace_printk.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 991bab9..d98789b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3555,8 +3555,10 @@
 #endif
 	}
 
-	if (mask == TRACE_ITER_PRINTK)
+	if (mask == TRACE_ITER_PRINTK) {
 		trace_printk_start_stop_comm(enabled);
+		trace_printk_control(enabled);
+	}
 
 	return 0;
 }