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

(cherry picked from commit e5de1d8dad25308f3a332f9386e05b851a36c507)