Revert "package/luvi: bump version to 2.8.0"

Revert "package/luvi: bump version to 2.8.0"

This reverts commit ac6fedda6b43996545ff498cd19a781698a96050.

Quoting Jörg Krause:
http://lists.busybox.net/pipermail/buildroot/2018-August/228534.html

"The version bump as version 2.8.0 does only updates the projects
 submodules, which we are not using at all. Instead, we always build
 luvi with dependencies provided as packages in Buildroot."

[Peter: drop autobuilder reference, issue is in luv, not luvi]
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>