staging: iio: adc: ad7280a: Avoid precedence issues in macro

Enclosing parameter with parenthesis due to avoid
possible precedence issue.
Signed-off-by: Cristian Sicilia <sicilia.cristian@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/adc/ad7280a.c

@@ -97,9 +97,10 @@
 #define AD7280A_NUM_CH			(AD7280A_AUX_ADC_6 - \
 					AD7280A_CELL_VOLTAGE_1 + 1)
 
-#define AD7280A_CALC_VOLTAGE_CHAN_NUM(d, c) ((d * AD7280A_CELLS_PER_DEV) + c)
-#define AD7280A_CALC_TEMP_CHAN_NUM(d, c)    ((d * AD7280A_CELLS_PER_DEV) + \
-					     c - AD7280A_CELLS_PER_DEV)
+#define AD7280A_CALC_VOLTAGE_CHAN_NUM(d, c) (((d) * AD7280A_CELLS_PER_DEV) + \
+					     (c))
+#define AD7280A_CALC_TEMP_CHAN_NUM(d, c)    (((d) * AD7280A_CELLS_PER_DEV) + \
+					     (c) - AD7280A_CELLS_PER_DEV)
 
 #define AD7280A_DEVADDR_MASTER		0
 #define AD7280A_DEVADDR_ALL		0x1F