Add a device tree for the Microsemi Luton PCB091 evaluation board.

It is based on the work of Lars Povlsen <lars.povlsen@microchip.com>.
Signed-off-by: NGregory CLEMENT <gregory.clement@bootlin.com>
Acked-by: NAlexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: NThomas Bogendoerfer <tsbogend@alpha.franken.de>