leds: ledtrig-heartbeat: Convert timers to use timer_setup()

Instead of using .data directly, convert to from_timer. Since the
trigger_data is allocated separately, the led_cdev must be explicitly
tracked for the callback.

Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Zhang Bo <bo.zhang@nxp.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-leds@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>