[SRU][B,F,G] update ENA driver, incl. new ethtool stats

[Kamal Mostafa]

BugLink: https://bugs.launchpad.net/bugs/1910291
    
Update Amazon ENA driver in {bionic,focal,groovy}-generic with latest
upstream commits from mainline applicable to each series, including
"net: ena: ethtool: Add new device statistics".

These commits are all mainline cherry-picks or trivial (file rename)
backports. Only the Amazon ENA driver is affected.

 -Kamal