target/loongarch: Fix GDB get the wrong pc

GDB LoongArch add a register orig_a0, see the base64.xml [1].
We should add the orig_a0 to match the upstream GDB.

[1]: https://github.com/bminor/binutils-gdb/blob/master/gdb/features/loongarch/base64.xml

Signed-off-by: Song Gao <gaosong@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220805033523.1416837-2-gaosong@loongson.cn>
3 files changed