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/ids8313_defconfig b/configs/ids8313_defconfig
index deafa38..7ae2f73 100644
--- a/configs/ids8313_defconfig
+++ b/configs/ids8313_defconfig
@@ -9,3 +9,4 @@
 CONFIG_AUTOBOOT_DELAY_STR="ids"
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_SYS_NS16550=y
+CONFIG_OF_LIBFDT=y