input: lm8323: fix attribute-creation race

Use the attribute groups of the led-class to create the time attribute
during probe in order to avoid racing with userspace.

Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>