staging: comedi: daqboard2000: rename reference DACs register macros

Rename the macros that define values for the reference DACs register to
avoid CamelCase, and to make it clearer which register they are
associated with.  Add a macro `DB2K_REG_DACS_SET` for the value `0x0080`
that triggers setting one of the references.
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>

drivers/staging/comedi/drivers/daqboard2000.c

@@ -244,8 +244,9 @@ static const struct comedi_lrange range_daqboard2000_ai = {
 #define DB2K_TRIG_CONTROL_DISABLE			0x0000
 
 /* Reference Dac Selection */
-#define DAQBOARD2000_PosRefDacSelect             0x0100
-#define DAQBOARD2000_NegRefDacSelect             0x0000
+#define DB2K_REF_DACS_SET				0x0080
+#define DB2K_REF_DACS_SELECT_POS_REF			0x0100
+#define DB2K_REF_DACS_SELECT_NEG_REF			0x0000
 
 struct daq200_boardtype {
 	const char *name;
@@ -569,7 +570,7 @@ static void daqboard2000_activateReferenceDacs(struct comedi_device *dev)
 	int timeout;
 
 	/*  Set the + reference dac value in the FPGA */
-	writew(0x80 | DAQBOARD2000_PosRefDacSelect,
+	writew(DB2K_REF_DACS_SET | DB2K_REF_DACS_SELECT_POS_REF,
 	       dev->mmio + DB2K_REG_REF_DACS);
 	for (timeout = 0; timeout < 20; timeout++) {
 		val = readw(dev->mmio + DB2K_REG_DAC_STATUS);
@@ -579,7 +580,7 @@ static void daqboard2000_activateReferenceDacs(struct comedi_device *dev)
 	}
 
 	/*  Set the - reference dac value in the FPGA */
-	writew(0x80 | DAQBOARD2000_NegRefDacSelect,
+	writew(DB2K_REF_DACS_SET | DB2K_REF_DACS_SELECT_NEG_REF,
 	       dev->mmio + DB2K_REG_REF_DACS);
 	for (timeout = 0; timeout < 20; timeout++) {
 		val = readw(dev->mmio + DB2K_REG_DAC_STATUS);