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/tseries_nand_defconfig b/configs/tseries_nand_defconfig
index 8151caf..5af033d 100644
--- a/configs/tseries_nand_defconfig
+++ b/configs/tseries_nand_defconfig
@@ -24,6 +24,7 @@
 CONFIG_CMD_TIME=y
 CONFIG_NETCONSOLE=y
 CONFIG_SYS_NS16550=y
+CONFIG_OF_LIBFDT=y
 CONFIG_USB=y
 CONFIG_USB_MUSB_HOST=y
 CONFIG_USB_STORAGE=y