iio: accel: fxls8962af: select IIO_BUFFER & IIO_KFIFO_BUF

Provide missing symbols to the module:
ERROR: modpost: iio_push_to_buffers [drivers/iio/accel/fxls8962af-core.ko] undefined!
ERROR: modpost: devm_iio_kfifo_buffer_setup_ext [drivers/iio/accel/fxls8962af-core.ko] undefined!

Cc: stable@vger.kernel.org
Fixes: 79e3a5bd

 ("iio: accel: fxls8962af: add hw buffered sampling")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Reviewed-by: Sean Nyekjaer <sean@geanix.com>
Link: https://lore.kernel.org/r/20240605203810.2908980-2-alexander.sverdlin@siemens.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>