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/TQM823L_LCD_defconfig b/configs/TQM823L_LCD_defconfig
index ebe9bdf..9a697c0 100644
--- a/configs/TQM823L_LCD_defconfig
+++ b/configs/TQM823L_LCD_defconfig
@@ -3,3 +3,4 @@
 CONFIG_TARGET_TQM823L=y
 CONFIG_SYS_EXTRA_OPTIONS="LCD,NEC_NL6448BC20"
 # CONFIG_CMD_SETEXPR is not set
+CONFIG_OF_LIBFDT=y