hv_netvsc: flag software created hash value

When the driver needs to create a hash value because it
was not done at higher level, then the hash should be marked
as a software not hardware hash.

Fixes: f72860af ("hv_netvsc: Exclude non-TCP port numbers from vRSS hashing")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>