tests/docker: Update docker-loongarch-cross toolchain

Update from clfs 5.0 to clfs 8.1, which includes updates
to binutils 2.41, gcc 13.2, and glibc 2.38.

See https://github.com/loongson/build-tools

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230829220228.928506-2-richard.henderson@linaro.org>
Message-Id: <20230914155422.426639-4-alex.bennee@linaro.org>

tests/docker/dockerfiles/debian-loongarch-cross.docker

@@ -20,7 +20,7 @@ RUN apt-get update && \
         git \
         python3-minimal
 
-RUN curl -#SL https://github.com/loongson/build-tools/releases/download/2022.05.29/loongarch64-clfs-5.0-cross-tools-gcc-glibc.tar.xz \
+RUN curl -#SL https://github.com/loongson/build-tools/releases/download/2023.08.08/CLFS-loongarch64-8.1-x86_64-cross-tools-gcc-glibc.tar.xz \
     | tar -xJC /opt
 
 ENV PATH $PATH:/opt/cross-tools/bin