gdb: LoongArch: Add Makefile, configure and NEWS

This commit adds Makefile, configure and NEWS for LoongArch.

Signed-off-by: Zhensong Liu <liuzhensong@loongson.cn>
Signed-off-by: Qing zhang <zhangqing@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>