Backport Amazon ENA ethernet driver version 2.0.2 from Linux 4.20
This mostly ammounts to cherry-picking the commits in the range described by
git log v4.19.5..v4.20-rc7 drivers/net/ethernet/amazon
Change e641e99f261f5203a911a9e0db54a214460d2cc4 introduced changes outside the
ena directory, but only removed a redundant #include and was trivial to scope
down.
Upstream dealt with merge conflicts in
d864991b220b7c62e81d21209e1fd978fd67352c; the resolution here was identical to
upstream.