Add (or make less ambiguous) the licensing of a number of files. 

Signed-off-by: Andy Pugh <andy@bodgesoc.org>
GPLv2+ is not a valid MODULE_LICENSE and using it breaks buildin
This commit attempts to fix that breakage

Signed-off-by: Andy Pugh <andy@bodgesoc.org>
docs: rebrand emc2 to linuxcnc in vfs11_vfd manpage