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/TQM5200_STK100_defconfig b/configs/TQM5200_STK100_defconfig
index 9e381f4..91e87d5 100644
--- a/configs/TQM5200_STK100_defconfig
+++ b/configs/TQM5200_STK100_defconfig
@@ -3,3 +3,4 @@
 CONFIG_TARGET_TQM5200=y
 CONFIG_SYS_EXTRA_OPTIONS="STK52XX_REV100"
 # CONFIG_CMD_SETEXPR is not set
+CONFIG_OF_LIBFDT=y