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/sc_sps_1_defconfig b/configs/sc_sps_1_defconfig
index a9aec82..06f2322 100644
--- a/configs/sc_sps_1_defconfig
+++ b/configs/sc_sps_1_defconfig
@@ -4,3 +4,4 @@
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_GPIO=y
+CONFIG_OF_LIBFDT=y