Revert "leds: handle suspend/resume in heartbeat trigger"

This reverts commit 5ab92a7c.

System cannot enter suspend mode because of heartbeat led trigger.
In autosleep_wq, try_to_suspend function will try to enter suspend
mode in specific period. it will get wakeup_count then call pm_notifier
chain callback function and freeze processes.
Heartbeat_pm_notifier is called and it call led_trigger_unregister to
change the trigger of led device to none. It will send uevent message
and the wakeup source count changed. As wakeup_count changed, suspend
will abort.

Fixes: 5ab92a7c ("leds: handle suspend/resume in heartbeat trigger")
Signed-off-by: Zhang Bo <bo.zhang@nxp.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>