staging: comedi: cb_pcimdas: fix handlers for DI and DO subdevices

staging: comedi: cb_pcimdas: fix handlers for DI and DO subdevices

Normally, low-level Comedi drivers set an `insn_bits` handler for
digital input (DI), digital output (DO) and digital input/output (DIO)
subdevice types to handle normal reading and writing of digital
channels.  The "cb_pcimdas" driver currently has an `insn_read` handler
for the DI subdevice and an `insn_write` handler for the DO subdevice.
However, the actual handler functions `cb_pcimdas_di_insn_read()` and
`cb_pcimdas_do_insn_write()` are written to behave like `insn_bits`
handlers.  Something's wrong there!  To fix it, set the functions as
`insn_bits` handlers and rename them for consistency.

Fixes: e56d03dee14a ("staging: comedi: cb_pcimdas: add main connector digital input/output")
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>