dt-bindings: power: reset: atmel,at91sam9260-shdwc: convert to yaml

Convert Microchip AT91 shutdown controller to YAML.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>