Staging: iio: release locks on error paths

There are a couple places here where we should have called
mutex_unlock() before returning.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/accel/adis16201_core.c

@@ -305,13 +305,17 @@ static int adis16201_read_raw(struct iio_dev *indio_dev,
 		mutex_lock(&indio_dev->mlock);
 		addr = adis16201_addresses[chan->address][0];
 		ret = adis16201_spi_read_reg_16(indio_dev, addr, &val16);
-		if (ret)
+		if (ret) {
+			mutex_unlock(&indio_dev->mlock);
 			return ret;
+		}
 
 		if (val16 & ADIS16201_ERROR_ACTIVE) {
 			ret = adis16201_check_status(indio_dev);
-			if (ret)
+			if (ret) {
+				mutex_unlock(&indio_dev->mlock);
 				return ret;
+			}
 		}
 		val16 = val16 & ((1 << chan->scan_type.realbits) - 1);
 		if (chan->scan_type.sign == 's')