hyperv: Add support for virtual Receive Side Scaling (vRSS)

This feature allows multiple channels to be used by each virtual NIC.
It is available on Hyper-V host 2012 R2.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>