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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/ingenic-adc.c

···
 	.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

···
 };
 module_platform_driver(ams_driver);
 
+MODULE_DESCRIPTION("Xilinx AMS driver");
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Xilinx, Inc.");

drivers/iio/buffer/kfifo_buf.c

···
 }
 EXPORT_SYMBOL_GPL(devm_iio_kfifo_buffer_setup_ext);
 
+MODULE_DESCRIPTION("Industrial I/O buffering based on kfifo");
 MODULE_LICENSE("GPL");