iio: adc: ti-ads1015: enable conversion when CONFIG_PM is not set

The ADS1015 device have two operating modes, continuous conversion mode
and single-shot mode.  This driver assumes that the continuous conversion
mode is selected by runtime resume callback when the ADC result is
requested.

If CONFIG_PM is disabled, the device is always in the default single-shot
mode and no one begins a single conversion.  So the conversion register
doesn't contain valid ADC result.  Fix it by changing the continuous mode
in probe function.

Cc: Daniel Baluta <daniel.baluta@gmail.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ti-ads1015.c

@@ -623,6 +623,13 @@ static int ads1015_probe(struct i2c_client *client,
  dev_err(&client->dev, "iio triggered buffer setup failed\n");
  return ret;
  }
+
+ ret = regmap_update_bits(data->regmap, ADS1015_CFG_REG,
+ ADS1015_CFG_MOD_MASK,
+ ADS1015_CONTINUOUS << ADS1015_CFG_MOD_SHIFT);
+ if (ret)
+ return ret;
+
  ret = pm_runtime_set_active(&client->dev);
  if (ret)
  goto err_buffer_cleanup;