iio: add missing MODULE_DESCRIPTION() macros

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/iio/adc/ingenic-adc.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/iio/adc/xilinx-ams.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/iio/buffer/kfifo_buf.o

Add the missing invocations of the MODULE_DESCRIPTION() macro.
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240607-md-drivers-iic-v1-1-9f9db6246083@quicinc.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ingenic-adc.c

@@ -920,4 +920,5 @@ static struct platform_driver ingenic_adc_driver = {
 	.probe = ingenic_adc_probe,
 };
 module_platform_driver(ingenic_adc_driver);
+MODULE_DESCRIPTION("ADC driver for the Ingenic JZ47xx SoCs");
 MODULE_LICENSE("GPL v2");

drivers/iio/adc/xilinx-ams.c

@@ -1430,5 +1430,6 @@ static struct platform_driver ams_driver = {
 };
 module_platform_driver(ams_driver);
 
+MODULE_DESCRIPTION("Xilinx AMS driver");
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Xilinx, Inc.");

drivers/iio/buffer/kfifo_buf.c

@@ -287,4 +287,5 @@ int devm_iio_kfifo_buffer_setup_ext(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(devm_iio_kfifo_buffer_setup_ext);
 
+MODULE_DESCRIPTION("Industrial I/O buffering based on kfifo");
 MODULE_LICENSE("GPL");