staging: iio: adc: Add paragraph to describe Kconfig symbol

This patch updates Kconfig with paragraph that describe config symbol
fully.Issue addressed by checkpatch.
Signed-off-by: Vatsala Narang <vatsalanarang@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/adc/Kconfig

@@ -12,6 +12,9 @@ config AD7816
 	  Say yes here to build support for Analog Devices AD7816/7/8
 	  temperature sensors and ADC.
 
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad7816.
+
 config AD7192
 	tristate "Analog Devices AD7190 AD7192 AD7193 AD7195 ADC driver"
 	depends on SPI