staging:iio:dac:ad5624r: Use strtobool for boolean values

Use strtobool for parsing the powerdown value instead of strict_strtol, since
the powerdown attribute is a boolean value.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/dac/ad5624r_spi.c

@@ -132,20 +132,18 @@ static ssize_t ad5624r_write_dac_powerdown(struct iio_dev *indio_dev,
 	uintptr_t private, const struct iio_chan_spec *chan, const char *buf,
 	size_t len)
 {
-	long readin;
+	bool pwr_down;
 	int ret;
 	struct ad5624r_state *st = iio_priv(indio_dev);
 
-	ret = strict_strtol(buf, 10, &readin);
+	ret = strtobool(buf, &pwr_down);
 	if (ret)
 		return ret;
 
-	if (readin == 1)
+	if (pwr_down)
 		st->pwr_down_mask |= (1 << chan->channel);
-	else if (!readin)
-		st->pwr_down_mask &= ~(1 << chan->channel);
 	else
-		ret = -EINVAL;
+		st->pwr_down_mask &= ~(1 << chan->channel);
 
 	ret = ad5624r_spi_write(st->us, AD5624R_CMD_POWERDOWN_DAC, 0,
 				(st->pwr_down_mode << 4) |