Update ENA version to v2.0.0

ENAv2 introduces many new features, bug fixes and improvements.

Main new features are LLQ (Low Latency Queues) and independent queues
reconfiguration using sysctl commands.

The year in copyright notice was updated to 2019.

Submitted by: Michal Krawczyk <mk@semihalf.com>
Obtained from: Semihalf
Sponsored by: Amazon, Inc.