LoongArch: ptrace: Expose hardware breakpoints to debuggers

Implement the regset-based ptrace interface that exposes hardware
breakpoints to user-space debuggers to query and set instruction and
data breakpoints.

Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>