leds/trigger/cpu: Move from CPU_STARTING to ONLINE level

There is no need the ledtriger to be called *that* early in the hotplug
process (+ with disabled interrupts). As explained by Jacek Anaszewski [0]
there is no need for it.
Therefore this patch moves it to the ONLINE/PREPARE_DOWN level using the
dynamic registration for the id.

[0] https://lkml.kernel.org/r/578C92BC.2070603@samsung.com

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: rt@linutronix.de
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-leds@vger.kernel.org
Link: http://lkml.kernel.org/r/1469028295-14702-1-git-send-email-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>