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/iio/Kconfig b/drivers/iio/Kconfig
index 345395e..397c8df 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -21,7 +21,7 @@
 if IIO_BUFFER
 
 config IIO_BUFFER_CB
-boolean "IIO callback buffer used for push in-kernel interfaces"
+	bool "IIO callback buffer used for push in-kernel interfaces"
 	help
 	  Should be selected by any drivers that do in-kernel push
 	  usage.  That is, those where the data is pushed to the consumer.
@@ -44,7 +44,7 @@
 endif # IIO_BUFFER
 
 config IIO_TRIGGER
-	boolean "Enable triggered sampling support"
+	bool "Enable triggered sampling support"
 	help
 	  Provides IIO core support for triggers.  Currently these
 	  are used to initialize capture of samples to push into