Fix ObsoleteFiles after ethernet driver removal

Fix OpsoleteFiles.inc after removal of ethernet drivers. The drivers have
manual pages, and manual pages are generally stored compressed, with a .gz
suffix, but this is not reflected in ObsoleteFiles and make delete-old fails
to remove them.

Approved by: brooks
Sponsored by: B3 Init
Differential Revision: https://reviews.freebsd.org/D20351