samples: move auxdisplay example code from Documentation

[SF Markus Elfring]

> Documentation/auxdisplay/cfag12864b needs to be updated to reflect the new
> home for the program (which probably does belong in samples/).
> 
> I wonder if these programs need MAINTAINERS entries too?

Do you find any more update suggestions interesting around this software module?
https://patchwork.kernel.org/project/LKML/list/?q=cfag12864b

Regards,
Markus