this is your network issue, try to clean this package and build again:
bitbake -c cleansstate sof-imx
bitbake sof-imx
I simply used a web browser to catch this file "sof-imx-1.8.0-1.tar.gz" and it worked.
So either there is a network problem on your side or the error message is misleading.
Could you please specify which BSP version you try to build?
Regards,
Bernhard.