iio:adc:twl6030: Enable measurement of VAC

VAC needs to be wired up to produce proper measurements,
without this change only near zero values are reported.
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Fixes: 1696f364 ("iio: twl6030-gpadc: TWL6030, TWL6032 GPADC driver")
Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Link: https://lore.kernel.org/r/20221217221305.671117-1-andreas@kemnade.infoSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/twl6030-gpadc.c

@@ -952,7 +952,7 @@ static int twl6030_gpadc_probe(struct platform_device *pdev)
 	}
 
 	ret = twl_i2c_write_u8(TWL6030_MODULE_ID0,
-				VBAT_MEAS | BB_MEAS | BB_MEAS,
+				VBAT_MEAS | BB_MEAS | VAC_MEAS,
 				TWL6030_MISC1);
 	if (ret < 0) {
 		dev_err(dev, "failed to wire up inputs\n");