enic: Add SRIOV support

This patch adds support to enable SRIOV on enic devices. Enic SRIOV VF's are dynamic vnics and will use the same driver code as dynamic vnics.

Signed-off-by: Roopa Prabhu <roprabhu@cisco.com>
Signed-off-by: Sujith Sankar <ssujith@cisco.com>
Signed-off-by: Christian Benvenuti <benve@cisco.com>
Signed-off-by: David Wang <dwang2@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>