ftrace: sched_switch plugin is deprecated

Actually, sched_switch function tracer is merged into wakeup/wakeup_rt
Update 'mini-HOWTO' for ftrace(Kernel function tracer).
If we want to trace "sched:sched_switch" to trace sched_switch func,
We may utilize event option.(e.g: trace-cmd list -e | grep sched)
This patch is based on Linux-3.3.rc2-SMP-PREEMPT

Link: http://lkml.kernel.org/r/1328695537-15081-1-git-send-email-geunsik.lim@gmail.com

Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Geunsik Lim <geunsik.lim@samsung.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -2764,12 +2764,12 @@ static const char readme_msg[] =
 	"tracing mini-HOWTO:\n\n"
 	"# mount -t debugfs nodev /sys/kernel/debug\n\n"
 	"# cat /sys/kernel/debug/tracing/available_tracers\n"
-	"wakeup preemptirqsoff preemptoff irqsoff function sched_switch nop\n\n"
+	"wakeup wakeup_rt preemptirqsoff preemptoff irqsoff function nop\n\n"
 	"# cat /sys/kernel/debug/tracing/current_tracer\n"
 	"nop\n"
-	"# echo sched_switch > /sys/kernel/debug/tracing/current_tracer\n"
+	"# echo wakeup > /sys/kernel/debug/tracing/current_tracer\n"
 	"# cat /sys/kernel/debug/tracing/current_tracer\n"
-	"sched_switch\n"
+	"wakeup\n"
 	"# cat /sys/kernel/debug/tracing/trace_options\n"
 	"noprint-parent nosym-offset nosym-addr noverbose\n"
 	"# echo print-parent > /sys/kernel/debug/tracing/trace_options\n"