virtchnl: Add filter data structures

This patch adds infrastructure to send virtchnl messages to the
PF to configure filters on the VF. The patch adds a struct
called virtchnl_filter which contains information about the fields
in the user-specified tc filter.

Signed-off-by: Harshitha Ramamurthy <harshitha.ramamurthy@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>