git: Fix kernel build without INET6.

[Thomas Nikolajsen]

>    The only issue left is that building with 'options SCTP' and without
>    'options INET6' is broken still (and was before -Werror), since our
>    SCTP code doesn't #ifdef out enough. But as our SCTP support is quite
>    old and has never been updated (and I don't plan to do so), I'll leave
>    it at that.
Both INET & INET6 needs to be in kernel when SCTP is used.
This is clealy stated in fbsd, where our SCTP is ported from.

You are absolutely right that our SCTP needs updating
(& netmp adaption); I have earlied said I would do it,
but it hasn't happened yet :-(

 -thomas