iio: adc: ad_sigma_delta: Remove unused variable 'ret'

Fixes the following W=1 kernel build warning(s):

 drivers/iio/adc/ad_sigma_delta.c: In function ‘ad_sd_trigger_handler’:
 drivers/iio/adc/ad_sigma_delta.c:405:6: warning: variable ‘ret’ set but not used [-Wunused-but-set-variable]
 405 | int ret;
 | ^~~

Cc: Michael Hennerich <Michael.Hennerich@analog.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad_sigma_delta.c

@@ -398,7 +398,6 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
 	unsigned int reg_size;
 	unsigned int data_reg;
 	uint8_t data[16];
-	int ret;
 
 	memset(data, 0x00, 16);
 
@@ -415,14 +414,12 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
 	case 4:
 	case 2:
 	case 1:
-		ret = ad_sd_read_reg_raw(sigma_delta, data_reg, reg_size,
-			&data[0]);
+		ad_sd_read_reg_raw(sigma_delta, data_reg, reg_size, &data[0]);
 		break;
 	case 3:
 		/* We store 24 bit samples in a 32 bit word. Keep the upper
 		 * byte set to zero. */
-		ret = ad_sd_read_reg_raw(sigma_delta, data_reg, reg_size,
-			&data[1]);
+		ad_sd_read_reg_raw(sigma_delta, data_reg, reg_size, &data[1]);
 		break;
 	}