board: lsxl: convert to DM_GPIO

Use the new mvebu GPIO driver and convert all the function calls to the
former kirkwood GPIO driver. This means that we are now using the LED
uclass and the regulator uclass. Unfortunately, the GPIO LED doesn't
offer a blinking method. Thus we are now stuck with solid on and off
states, which makes debugging a bit harder. Also, there is no GPIO fan
driver for now.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Stefan Roese <sr@denx.de>