staging: comedi: cb_pcimdas: tidy up cb_pcimdas_auto_attach()

For aesthetics, add some whitespace to the subdevice init.

Remove the unnecessary comments as well as the initialization of the
analog input subdevice 'len_chanlist'. That member is only used by
subdevices that support async commands.

For aesthetics, rename the analog input subdevice (*insn_read) function.

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>