Update ENA driver man page
Bring the obsolete man page up to date:
- update diagnostic error messages
- add documentation of loader tunables
- document netmap support
- add a driver history section
- update the contact information
Submitted by: Artur Rojek <ar@semihalf.com>
Submitted by: Michal Krawczyk <mk@semihalf.com>
Obtained from: Semihalf
MFC after: 2 weeks
Sponsored by: Amazon, Inc.