MIPS: Loongson64: Add a Loongson-2K1000 default config file

Add default config for Loongson-2K1000.

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>