staging: comedi: usbduxsigma: rewrite "Devices:" line

Rewrite the "Devices:" line in the comedi "driver" comment to conform to
the usual comedi format for this line.  The line should be a
comma-separated list where the first item is in the following format:

  [Manufacturer] BOARD-NAME (comedi-board-name)

The "[Manufacturer]" and/or "(comedi-board-name)" parts may be omitted
from following items, in which case the parts from the preceding item
are used.  The "Devices:" line may be continued continued over several
lines by using one or more spaces at the start of each continuation line
(not counting the space after the "*" in the block comment).

Also change "USB-DUX" to "USB-DUX-SIGMA" to distinguish it from the
other USB-DUX models.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>