VME: Move API documentation to Documentation folder

The documentation for the VME device driver API is currently in
drivers/vme/vme_api.txt, move this to Documentation/vme_api.txt
Signed-of-by: Martyn Welch <martyn.welch@ge.com>
Acked-by: Rob Landley <rob@landley.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>