iio: adc: Revert "axp288: Drop bogus AXP288_ADC_TS_PIN_CTRL register modifications"

Inheriting the ADC BIAS current settings from the BIOS instead of
hardcoding then causes the AXP288 to disable charging (I think it
mis-detects an overheated battery) on at least one model tablet.

So lets go back to hard coding the values, this reverts
commit fa2849e9 ("iio: adc: axp288: Drop bogus
AXP288_ADC_TS_PIN_CTRL register modifications"), fixing charging not
working on the model tablet in question.

The exact cause is not fully understood, hence the revert to a known working
state.

Cc: stable@vger.kernel.org
Reported-by: Umberto Ixxo <sfumato1977@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>