staging: comedi: das1800: add missing break in switch

Commit 06ad6bd8 "staging: comedi: das1800: cleanup das1800_probe()"

Accidently removed the 'break' statement for case 0x8 of the switch.
Add it back.

Reported-by: coverity (CID 1309550)
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>