iio: adc: ad4000: fix backported MODULE_IMPORT_NS

Fix compile error due to backported MODULE_IMPORT_NS(). The 6.6 kernel
expects the argument to this to not be quoted while newer kernels
expect it to be quoted.

When we backported commit 59b51ed ("iio: adc: ad4000: Add support
for SPI offload") we missed adapting this difference.

Signed-off-by: David Lechner <dlechner@baylibre.com>

Author: dlech

drivers/iio/adc/ad4000.c

@@ -1260,4 +1260,4 @@ module_spi_driver(ad4000_driver);
 MODULE_AUTHOR("Marcelo Schmitt <marcelo.schmitt@analog.com>");
 MODULE_DESCRIPTION("Analog Devices AD4000 ADC driver");
 MODULE_LICENSE("GPL");
-MODULE_IMPORT_NS("IIO_DMAENGINE_BUFFER");
+MODULE_IMPORT_NS(IIO_DMAENGINE_BUFFER);