uboot-imx

dm: led: Adjust the LED uclass

At present this is very simple, supporting only on and off. We want to
also support toggling and blinking. As a first step, change the name of
the main method and use an enum to indicate the state.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Ziping Chen <techping.chan@gmail.com>