staging: comedi: gsc_hpdi: update driver description comment

Reformat the comment used to describe the Comedi driver to use the usual
block comment style.

Update the information reflecting the fact that the driver no longer
supports manual attachment of devices via the `COMEDI_DEVCONFIG` ioctl.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>