iio: adc: twl4030_madc: Fix description of twl4030_madc_set_current_generator()

The @chan parameter can be 0 or 1 and not a bit mask. Fix wrong description.
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Marek Belisko <marek@goldelico.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/twl4030-madc.c

@@ -662,10 +662,8 @@ EXPORT_SYMBOL_GPL(twl4030_get_madc_conversion);
  *
  * @madc:	pointer to twl4030_madc_data struct
  * @chan:	can be one of the two values:
- *		TWL4030_BCI_ITHEN
- *		Enables bias current for main battery type reading
- *		TWL4030_BCI_TYPEN
- *		Enables bias current for main battery temperature sensing
+ *		0 - Enables bias current for main battery type reading
+ *		1 - Enables bias current for main battery temperature sensing
  * @on:		enable or disable chan.
  *
  * Function to enable or disable bias current for