idpf: move virtchnl structures to the header file

Move virtchnl structures to the header file to expose them for the PTP
virtchnl file.

Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Milena Olech <milena.olech@intel.com>
Tested-by: Mina Almasry <almasrymina@google.com>
Tested-by: Samuel Salin <Samuel.salin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>