virtchnl is a protocol/interface specification that allows the Intel
"Adaptive Virtual Function (AVF)" driver (iavf.ko) to work with more than
one physical function driver. The AVF driver sends "virtchnl commands"
(control plane only) to the PF driver over mailbox queues and the PF driver
executes these commands and returns a result to the VF, again over mailbox.
This patch adds AVF support for the ice PF driver by implementing the
following virtchnl commands: