This change updates the arguments passed to the validate function
and fixes the caller, as well as uses the new return values added to
virtchnl.h

One other minor tweak, remove a duplicate set to zero of valid_len.

This is in preparation for moving the function to virtchnl.h.
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>