iio: adc: ad7944: add support for SPI offload

Add support for SPI offload to the ad7944 driver. This allows reading
data at the max sample rate of 2.5 MSPS.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250207-dlech-mainline-spi-engine-offload-2-v8-11-e48a489be48c@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: dlech

drivers/iio/adc/Kconfig

@@ -381,6 +381,9 @@ config AD7923
 config AD7944
 	tristate "Analog Devices AD7944 and similar ADCs driver"
 	depends on SPI
+	select SPI_OFFLOAD
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
 	help
 	  Say yes here to build support for Analog Devices
 	  AD7944, AD7985, AD7986 ADCs.