r339585:
    Do not drop UDP traffic when TXCSUM_IPV6 flag is on

    PR:             [[ https://bugs.freebsd.org/231797 | 231797 ]]
    Submitted by:   whu
    Reviewed by:    dexuan
    Obtained from:  Kevin Morse
    Sponsored by:   Microsoft
    Differential Revision:  https://bugs.freebsd.org/bugzilla/attachment.cgi?id=198333&action=diff