ftrace-graph: Remove usage of ftrace_stop() in ftrace_graph_stop()

All archs now use ftrace_graph_is_dead() to stop function graph
tracing. Remove the usage of ftrace_stop() as that is no longer
needed.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_functions_graph.c

@@ -40,11 +40,6 @@ bool ftrace_graph_is_dead(void)
 void ftrace_graph_stop(void)
 {
 	kill_ftrace_graph = true;
-	/*
-	 * ftrace_stop() will be removed when all archs are updated to
-	 * use ftrace_graph_is_dead()
-	 */
-	ftrace_stop();
 }
 
 /* When set, irq functions will be ignored */