staging: comedi: pcmmio: remove 'iobases' from the subdevice private data

This member of the subdevice private data is not longer used. Remove it.

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>