loongson/pypi: links for preshed

INFO: Because this project isn't in the mirror_whitelist, no releases from root/pypi are included.

loongson/pypi preshed-3.0.2-cp37-cp37m-linux_loongarch64.whl
loongson/pypi preshed-3.0.2-cp27-cp27mu-linux_loongarch64.whl
loongson/pypi preshed-2.0.1-cp37-cp37m-linux_loongarch64.whl
loongson/pypi preshed-2.0.1-cp27-cp27mu-linux_loongarch64.whl