You can uninstall or removes an installed ata-modules-4.7.0-1-powerpc64l package itself from Debian 9 (Stretch) through the terminal,
$ sudo apt-get remove ata-modules-4.7.0-1-powerpc64l
If you would like to remove ata-modules-4.7.0-1-powerpc64l and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove ata-modules-4.7.0-1-powerpc64l
If you use with purge options to ata-modules-4.7.0-1-powerpc64l package all the configuration and dependent packages will be removed.
$ sudo apt-get purge ata-modules-4.7.0-1-powerpc64l
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove ata-modules-4.7.0-1-powerpc64l