ixl: Fix mbuf hash type settings.

[sepherosa_gmail.com]

Summary

IPV6_EXs in RSS never mean fragment.  They mean:
"- Home address from the home address option in the IPv6 destination
   options header.  If the extension header is not present, use the
   Source IPv6 Address.
 - IPv6 address that is contained in the Routing-Header-Type-2 from
   the associated extension header.  If the extension header is not
   present, use the Destination IPv6 Address."

UDP_IPV4_EX is an invalid RSS hash type, which will be removed.

Quoted from:
https://docs.microsoft.com/en-us/windows-hardware/drivers/network/rss-hashing-types#ndishashipv6ex

[sbruno]

Did microsoft update the referenced link? I don't see the removal notice in it.

[sepherosa_gmail.com]

In D12450#258277, @sbruno wrote:

Did microsoft update the referenced link? I don't see the removal notice in it.

The UDP_IPV4_EX was never defined. FreeBSD defined it by mistake.