staging: comedi: cb_pcidas: tidy up memory subdevice init

For aesthetics, add some whitespace to the initialization of this
subdevice.

Rename the (*insn_read) function so it has namespace associated with
the driver.

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>