kernel: Mark some contigfree()/kfree() arguments as "never NULL".

Those are contigfree()'s addr and kfree()'s addr and type.
contigfree()'s type isn't actually used by the function.
vnconfig - don't make it harder to script vnconfig

 * There's no real need to be printing the "Using" in front of what
   anyone *really* cares about.
udevd - fix realloc usage