igb: Add support for enabling VFs to PF driver.

This patch adds the support to handle requests from the VF to perform
operations such as completing resets, setting/reading mac address, adding
vlans, adding multicast addresses, setting rlpml, and general
communications between the PF and all VFs.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>