ARM: configs: at91: sama5: Enable CLASSD

CLASSD is present on SAMA5d2 SoCs.

Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200618154147.687878-1-codrin.ciubotariu@microchip.com