staging: comedi: daqboard2000: use macros from "plx9080.h"

The Daqboard/2000 uses a PLX PCI-9080 chip to interface with the PCI
bus.  The "daqboard2000" driver uses the PCI-9080 "CNTRL" register to
perform various tasks, but defines its own macros for the register
values.  Use the macros from "plx9080.h" instead.  The various functions
that change the CNTRL register just wiggle individual bits up and down,
but they ignore the current register value - the old macros defined the
full value to be written to the register.  Change them to read and
modify the register value.

Also remove a read of the CNTRL register in `daqboard2000_auto_attach()`
where the value is just thrown away, as it seems to serve no purpose
there (such as flushing PCI writes).

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>