staging: comedi: ii_pci20kc.c: cleanup the dio subdevice

For asethetics, redefine the register map for the carrier board.
The 'PCI*' names lead one to think this is a PCI board not a
legacy ISA board.

Remove the #if 0'd out pci20xxx_{do,di}() functions. They are not
needed.

Rename, and fix, the pci20xxx_dio_config() function. The control
and direction registers are not readable. Use the new register map
defines instead of the crazy bit shifts.

Rename, and fix, the pci20xxx_dio_insn_config() function. This
function should treat data[0] as the 'instruction' to handle not
just use it to determine if the port is an input or output.

Rename, and tix, the pci20xxx_dio_insn_bits() function. The 'state'
only needs to be updated if the 'mask' indicates.

For aesthetics, abosrb the pci20xxx_dio_init() into the (*attach)
function.

Fix the carrier board id detect in the (*attach). There are two carrier
board types, one with 32 dio channels and one without. Use this info
when setting up the dio subdevice.
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>