hyperv/hn: Trust host TCP segment checksum verification by default.

According to all available information, VMSWITCH always does the
TCP segment checksum verification before sending the segment to
guest.

Reviewed by: adrian, delphij, Hongjiang Zhang <honzhan microsoft com>
Approved by: adrian (mentor)
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D4991