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/usb/phy/Kconfig b/drivers/usb/phy/Kconfig
index c6d0c8e74..52d3d58 100644
--- a/drivers/usb/phy/Kconfig
+++ b/drivers/usb/phy/Kconfig
@@ -119,7 +119,7 @@
 
 config TAHVO_USB_HOST_BY_DEFAULT
 	depends on TAHVO_USB
-	boolean "Device in USB host mode by default"
+	bool "Device in USB host mode by default"
 	help
 	  Say Y here, if you want the device to enter USB host mode
 	  by default on bootup.