Hyper-V: hn: Store host hash value in flowid

When rx packet contains hash value sent from host, store it in
the mbuf's flowid field so when the same mbuf is on the tx path,
the hash value can be used by the host to determine the outgoing
network queue.

MFC after: 2 weeks
Sponsored by: Microsoft

(cherry picked from commit 80f39bd95f22322152709ea5fae3a3c546044c9c)