staging: comedi: mf6x4: tidy up subdevice init

For aesthetics, add some whitespace to the subdevice initialization.

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