staging: comedi: cb_pcidda: check for subdev_8255_init() failure

The subdev_8255_init() can fail, make sure to check for it.

This board has two 8255 subdevices, one at iobase PCI bar2 and one
at iobase PCI bar2 + 4. Init the subdevices using a for() loop to
make the code a bit more concise.

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>