kconfig: use bool instead of boolean for type definition attributes

Support for keyword 'boolean' will be dropped later on.

No functional change.

Reference: http://lkml.kernel.org/r/cover.1418003065.git.cj@linux.com
Signed-off-by: Christoph Jaeger <cj@linux.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/drivers/staging/iio/Kconfig b/drivers/staging/iio/Kconfig
index fa38be0..2418302 100644
--- a/drivers/staging/iio/Kconfig
+++ b/drivers/staging/iio/Kconfig
@@ -30,13 +30,13 @@
 if IIO_SIMPLE_DUMMY
 
 config IIO_SIMPLE_DUMMY_EVENTS
-       boolean "Event generation support"
+       bool "Event generation support"
        select IIO_DUMMY_EVGEN
        help
          Add some dummy events to the simple dummy driver.
 
 config IIO_SIMPLE_DUMMY_BUFFER
-	boolean "Buffered capture support"
+	bool "Buffered capture support"
 	select IIO_BUFFER
 	select IIO_KFIFO_BUF
 	help