iio: addac: Kconfig: update ad74413r selections

Building ad74413r without selecting IIO_BUFFER and
IIO_TRIGGERED_BUFFER generates error with respect to the iio trigger
functions that are used within the driver.
Update the Kconfig accordingly.

Fixes: fea251b6

 ("iio: addac: add AD74413R driver")
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Link: https://lore.kernel.org/r/20230912085421.51102-1-antoniu.miclaus@analog.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>