iio: adc: max11410: fix incomplete vref buffer mask

VREFP bit was missing from channel configuration mask and VREFN bit was
included twice instead which fails to enable positive reference buffer when
requested by a channel. Channels that don't enable vrefp buffer were not
affected.

Fixes: a44ef7c4 ("iio: adc: add max11410 adc driver")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Ibrahim Tilki <Ibrahim.Tilki@analog.com>
Link: https://lore.kernel.org/r/20221122114718.17557-1-Ibrahim.Tilki@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/max11410.c

@@ -370,7 +370,7 @@ static int max11410_configure_channel(struct max11410_state *st,
 		 FIELD_PREP(MAX11410_CTRL_UNIPOLAR_BIT, cfg.bipolar ? 0 : 1);
 	ret = regmap_update_bits(st->regmap, MAX11410_REG_CTRL,
 				 MAX11410_CTRL_REFSEL_MASK |
-				 MAX11410_CTRL_VREFN_BUF_BIT |
+				 MAX11410_CTRL_VREFP_BUF_BIT |
 				 MAX11410_CTRL_VREFN_BUF_BIT |
 				 MAX11410_CTRL_UNIPOLAR_BIT, regval);
 	if (ret)