dt-bindings: arm: rockchip: Add NanoPC T6

Add the NanoPC T6, a single board computer from FriendlyElec

Signed-off-by: Thomas McKahan <tmckahan@singleboardsolutions.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230809112120.99-2-tmckahan@singleboardsolutions.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>