iio: resolver: ad2s1210: add missing select (TRIGGERED_)BUFFER in Kconfig

iio: resolver: ad2s1210: add missing select (TRIGGERED_)BUFFER in Kconfig

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

Add the missing 'select IIO_BUFFER' and 'select IIO_TRIGGERED_BUFFER'.

Fixes: 128b9389db0e ("staging: iio: resolver: ad2s1210: add triggered buffer support")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20241003-ad2s1210-select-v1-2-4019453f8c33@gmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>