ixgbe: update if_sriov to use the new mailbox apis

This fixes a page fault when creating VFs and updates to the new mailbox
API and naming conventions.

The functionality works to the same level that it did before my recent
changes. In particular on my 82599 it creates both passthru and ixv
interfaces. In either case, the PF seems to lose the ability to pass
traffic. The ixv driver fails to attach. These issues are present with
or without my updates.

If you use SR-IOV on ixgbe I would be interested in hearing what does
or does not work for you.

(cherry picked from commit 36c516b31136f645472c12d8597534656272acd6)