MIPS: Loongson64: DeviceTree for Loongson-2K1000

Add DeviceTree files for Loongson-2K1000 processor, currently only
supports single-core boot.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Tested-by: Ming Wang <wangming01@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>