staging: comedi: jr3_pci: 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
and `attach()` method.

Also, in the instructions indicating where to put the firmware file,
mention the expected name of the file since the driver requests the
firmware file by name.

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