staging: comedi: addi_apci_1516: cleanup the subdevice init

For aesthetic reasons. add some whitespace to the subdevice init.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>