staging: iio: adc: ad7280a: handle error from __ad7280_read32()

Inside __ad7280_read32(), the spi_sync_transfer() can fail with negative
error code. This change will ensure that this error is being passed up
in the call stack, so it can be handled.
Signed-off-by: Slawomir Stepien <sst@poczta.fm>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/adc/ad7280a.c

@@ -256,7 +256,9 @@ static int ad7280_read(struct ad7280_state *st, unsigned int devaddr,
 	if (ret)
 		return ret;
 
-	__ad7280_read32(st, &tmp);
+	ret = __ad7280_read32(st, &tmp);
+	if (ret)
+		return ret;
 
 	if (ad7280_check_crc(st, tmp))
 		return -EIO;
@@ -294,7 +296,9 @@ static int ad7280_read_channel(struct ad7280_state *st, unsigned int devaddr,
 
 	ad7280_delay(st);
 
-	__ad7280_read32(st, &tmp);
+	ret = __ad7280_read32(st, &tmp);
+	if (ret)
+		return ret;
 
 	if (ad7280_check_crc(st, tmp))
 		return -EIO;
@@ -327,7 +331,9 @@ static int ad7280_read_all_channels(struct ad7280_state *st, unsigned int cnt,
 	ad7280_delay(st);
 
 	for (i = 0; i < cnt; i++) {
-		__ad7280_read32(st, &tmp);
+		ret = __ad7280_read32(st, &tmp);
+		if (ret)
+			return ret;
 
 		if (ad7280_check_crc(st, tmp))
 			return -EIO;
@@ -370,7 +376,10 @@ static int ad7280_chain_setup(struct ad7280_state *st)
 		return ret;
 
 	for (n = 0; n <= AD7280A_MAX_CHAIN; n++) {
-		__ad7280_read32(st, &val);
+		ret = __ad7280_read32(st, &val);
+		if (ret)
+			return ret;
+
 		if (val == 0)
 			return n - 1;