bhyve: validate e82545 checksum offset field

Reported by: Mehdi Talbi, Synacktiv

(cherry picked from commit b0aa20bec5db244980a0248e24dd6b8e1e68c4d0)
(cherry picked from commit 53f72209479885dfa6a7e6ed68cbc82c68464f4b)
(cherry picked from commit 1da62e16e4a2270c85db1f507cc3025c5e0d9fdd)

Approved by: so
Security: CVE-2022-23087
Security: FreeBSD-SA-22:05.bhyve