ixgbe: Add missing mailbox API 1.6 definitionstable/14

The SR-IOV status change reports mailbox API 1.6 but omitted its enum
definition, leaving main unable to compile.

API 1.6 is an established ixgbe mailbox wire revision.  Add it at the
end of the revision enum, before the unknown sentinel as required by
the stable numbering contract.  Naming the revision does not enable
negotiation or operations which will come with the E610 support.

Reported by:	Herbert J. Skuhra <herbert@gojira.at>

(cherry picked from commit 6a1703c112ff2904feb39288f0746c8f0a04f938)

0 files changed, 0 insertions, 0 deletions