ixgbe: Add mailbox API version negotiation support to ixgbe PF

This change allows us to add a mailbox versioning API.  This will allow us
to determine the features supported by the VFs from the PF.  For example we
will be implementing a version 1.1 API for the VF that will indicate that
it can support us enabling Jumbo frames as the VF will support buffer
chaining.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Tested-by: Robert Garrett <RobertX.Garrett@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe.h

@@ -135,6 +135,7 @@ struct vf_data_storage {
 	u16 tx_rate;
 	u16 vlan_count;
 	u8 spoofchk_enabled;
+	unsigned int vf_api;
 };
 
 struct vf_macvlans {