Bug#1069797: openmsx: please add support for loong64

[zhangdandan]

Hi maintainer,

please consider to add loongarch64 support in openmsx source package.

LoongArch64 was supported in openmsx's upstream:

https://github.com/openMSX/openMSX/commit/d77fe49007a72594b273cd6077537de6e6d77118

Dandan