virtchnl: Add header dependencies

The <linux/avf/virtchnl.h> uses BIT, struct_size and ETH_ALEN macros
but does not include appropriate header files that defines them.
Add these dependencies so this header file can be included anywhere.

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>