Staging: iio: adc: Update Kconfig entries adding module name information

This patch fixes the following checkpatch.pl warning:

WARNING: please write a paragraph that describes the config symbol fully
Signed-off-by: Vaishali Thakkar <vthakkar1994@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/adc/Kconfig

@@ -22,6 +22,9 @@ config AD7606_IFACE_PARALLEL
 	  Say yes here to include parallel interface support on the AD7606
 	  ADC driver.
 
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad7606_iface_parallel.
+
 config AD7606_IFACE_SPI
 	tristate "spi interface support"
 	depends on AD7606
@@ -30,6 +33,9 @@ config AD7606_IFACE_SPI
 	  Say yes here to include parallel interface support on the AD7606
 	  ADC driver.
 
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad7606_iface_spi.
+
 config AD7780
 	tristate "Analog Devices AD7780 and similar ADCs driver"
 	depends on SPI
@@ -107,4 +113,6 @@ config SPEAR_ADC
 	  Say yes here to build support for the integrated ADC inside the
 	  ST SPEAr SoC. Provides direct access via sysfs.
 
+	  To compile this driver as a module, choose M here: the
+	  module will be called spear_adc.
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