tracing: Move enabling tracepoints to just after rcu_init()

tracing: Move enabling tracepoints to just after rcu_init()

Enabling tracepoints at boot up can be very useful. The tracepoint
can be initialized right after RCU has been. There's no need to
wait for the early_initcall() to be called. That's too late for some
things that can use tracepoints for debugging. Move the logic to
enable tracepoints out of the initcalls and into init/main.c to
right after rcu_init().

This also allows trace_printk() to be used early too.

Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1412121539300.16494@nanos
Link: http://lkml.kernel.org/r/[email protected]
Reviewed-by: Paul E. McKenney <[email protected]>
Suggested-by: Thomas Gleixner <[email protected]>
Tested-by: Thomas Gleixner <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>