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/meesc_defconfig b/configs/meesc_defconfig
index 7d1fe7b..b63712d 100644
--- a/configs/meesc_defconfig
+++ b/configs/meesc_defconfig
@@ -7,3 +7,4 @@
 # CONFIG_CMD_LOADS is not set
 # CONFIG_CMD_FPGA is not set
 # CONFIG_CMD_SETEXPR is not set
+CONFIG_OF_LIBFDT=y