netvsc: need napi scheduled during removal

Since rndis_halt_device waits until all outstanding sends and
receives are completed. Netvsc device needs to still schedule
NAPI to see those completions.

Fixes: 2506b1dc4bbe ("netvsc: implement NAPI")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>