hv_netvsc: Add error handling while switching data path

Add error handling in case of failure to send switching data path message
to the host.

Reported-by: Shachar Raindel <shacharr@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>