staging: comedi: ni_stc.h: tidy up DAC[01]_Direct_Data registers

Rename the CamelCase and convert the defines into a macro.
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>

drivers/staging/comedi/drivers/ni_mio_common.c

@@ -2733,7 +2733,7 @@ static int ni_ao_insn_write(struct comedi_device *dev,
 	} else if (devpriv->is_m_series) {
 		reg = NI_M_DAC_DIRECT_DATA_REG(chan);
 	} else {
-		reg = (chan) ? DAC1_Direct_Data : DAC0_Direct_Data;
+		reg = NI_E_DAC_DIRECT_DATA_REG(chan);
 	}
 
 	ni_ao_config_chanlist(dev, s, &insn->chanspec, 1, 0);

drivers/staging/comedi/drivers/ni_stc.h

@@ -638,13 +638,13 @@ static inline unsigned GPCT_DMA_Select_Mask(unsigned gpct_index)
 #define NI_E_AO_DEGLITCH		BIT(1)
 #define NI_E_AO_CFG_BIP			BIT(0)
 
+#define NI_E_DAC_DIRECT_DATA_REG(x)	(0x18 + ((x) * 2)) /* w16 */
+
 #define NI_E_8255_BASE			0x19	/* rw8 */
 
 #define NI_E_AI_FIFO_DATA_REG		0x1c	/* r16 */
 
 #define NI_E_AO_FIFO_DATA_REG		0x1e	/* w16 */
-#define DAC0_Direct_Data		0x18
-#define DAC1_Direct_Data		0x1a
 
 /* 611x registers (these boards differ from the e-series) */