iio:dummy: Add extra paragraphs on Kconfig

This patch fixes the checkpatch.pl warning:

drivers/iio/dummy/Kconfig:21: WARNING: please write a paragraph that
describes the config symbol fully
drivers/iio/dummy/Kconfig:27: WARNING: please write a paragraph that
describes the config symbol fully

This patch expands the explanation about IIO_DUMMY_EVGEN by using the
code documentation found in iio/dummy/iio_dummy_evgen.c. In the same
way, the information related to IIO_SIMPLE_DUMMY_BUFFER was extracted
from file iio_simple_dummy_buffer.c.

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dummy/Kconfig

@@ -24,6 +24,10 @@ config IIO_SIMPLE_DUMMY_EVENTS
 	help
 	  Add some dummy events to the simple dummy driver.
 
+	  The purpose of this is to generate 'fake' event interrupts thus
+	  allowing that driver's code to be as close as possible to that
+	  a normal driver talking to hardware.
+
 config IIO_SIMPLE_DUMMY_BUFFER
 	bool "Buffered capture support"
 	select IIO_BUFFER
@@ -32,6 +36,9 @@ config IIO_SIMPLE_DUMMY_BUFFER
 	help
 	  Add buffered data capture to the simple dummy driver.
 
+	  Buffer handling elements of industrial I/O reference driver.
+	  Uses the kfifo buffer.
+
 endif # IIO_SIMPLE_DUMMY
 
 endmenu