iio: adc: ti-ads8688: add missing select IIO_(TRIGGERED_)BUFFER in Kconfig

iio: adc: ti-ads8688: add missing select IIO_(TRIGGERED_)BUFFER in Kconfig

commit 4c4834fd8696a949d1b1f1c2c5b96e1ad2083b02 upstream.

This driver makes use of triggered buffers, but does not select the
required modules.

Fixes: 2a86487786b5 ("iio: adc: ti-ads8688: add trigger and buffer support")
Add the missing 'select IIO_BUFFER' and 'select IIO_TRIGGERED_BUFFER'.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Reviewed-by: Sean Nyekjaer <sean@geanix.com>
Link: https://patch.msgid.link/20241003-iio-select-v1-4-67c0385197cd@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>