e6000sw.4: Add HISTORY

MFC after: 3 days
Reviewed by: mhorne
Approved by: mhorne (mentor)
Approved by: re (cperciva)
Differential Revision: https://reviews.freebsd.org/D50358

(cherry picked from commit c808bee35b1129abd9af137204ebd15559b90b5b)
(cherry picked from commit 6426b01310122c7563d982ec21c91b98f3f5bd3b)