if_link: Add SR-IOV configuration methods

Add SR-IOV VF management methods to IFLA_LINKINFO. This allows userspace to
use rtnetlink to configure VF network devices.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>