ena: fix man page typos and update contact section

Verified spelling in the README and fixed the typos.

Also updated the contact section by removing Artur and adding Dawid
Gorecki who is now the second ENA FreeBSD driver developer.

Submitted by: Michal Krawczyk <mk@semihalf.com>
Obtained from: Semihalf
MFC after: 2 weeks
Sponsored by: Amazon, Inc.