Instead, please get official APM versions of the UEFI firmware from myapm.apm.com.
mustang_uefi_upgrade.tar.gz is a tarball containing files, tools, scripts, and documentation on upgrading an X-Gene C1 from the default u-boot install to UEFI. Contact Mark Langsdorf (email@example.com) if you have difficulties.
If you need to do your own firmware development, the repository is still available at https://github.com/mlangsdorf/linaro-edk2/tree/rh-0.16-devel. However, it is not guaranteed to be up to date or supported.