gdbserver: LoongArch: Add orig_a0 processing

Commit 736918239b16 ("gdb: LoongArch: add orig_a0 into register set")
introduced orig_a0, similar processing needs to be done in gdbserver.

At the same time, add orig_a0 related comments.

Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
2 files changed