virtchnl: Add compile time static asserts to validate structure sizes

This uses preprocessor tricks to make sure that a divide by zero
occurs if a struct changes size outside the expected number of
bytes.

Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
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>