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/cam5200_defconfig b/configs/cam5200_defconfig
index eda131a..77fbeb2 100644
--- a/configs/cam5200_defconfig
+++ b/configs/cam5200_defconfig
@@ -3,3 +3,4 @@
 CONFIG_TARGET_TQM5200=y
 CONFIG_SYS_EXTRA_OPTIONS="CAM5200,TQM5200S,TQM5200_B"
 # CONFIG_CMD_SETEXPR is not set
+CONFIG_OF_LIBFDT=y