staging: comedi: cb_pcidas: check for failure of subdev_8255_init

It's possible for subdev_8255_init() to fail due to its kzalloc().
Make sure to check for this failure and pass on the error code.

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>