hv_netvsc: Use Windows version instead of NVSP version on GPAD teardown

When changing network interface settings, Windows guests
older than WS2016 can no longer shutdown. This was addressed
by commit 0ef58b0a ("hv_netvsc: change GPAD teardown order
on older versions"), however the issue also occurs on WS2012
guests that share NVSP protocol versions with WS2016 guests.
Hence we use Windows version directly to differentiate them.

Fixes: 0ef58b0a

 ("hv_netvsc: change GPAD teardown order on older versions")
Signed-off-by: Mohammed Gamal <mgamal@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>