ena: Update driver version to v2.6.2

Bug Fixes:

• Remove timer service re-arm on ena_restore_device failure.
• Re-Enable per-packet missing tx completion print

Minor Changes:

• Switch driver owners from Semihalf to Amazon in man file.

MFC after: 2 weeks
Sponsored by: Amazon, Inc.
Pull Request: https://github.com/freebsd/freebsd-src/pull/637