Move CONFIG_OF_LIBFDT to Kconfig

Move this option to Kconfig and tidy up existing boards.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/kmcoge5ne_defconfig b/configs/kmcoge5ne_defconfig
index 6623162..ca13a26 100644
--- a/configs/kmcoge5ne_defconfig
+++ b/configs/kmcoge5ne_defconfig
@@ -3,3 +3,4 @@
 CONFIG_TARGET_KM8360=y
 CONFIG_SYS_EXTRA_OPTIONS="KMCOGE5NE"
 CONFIG_SYS_NS16550=y
+CONFIG_OF_LIBFDT=y