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/ls1043aqds_nor_ddr3_defconfig b/configs/ls1043aqds_nor_ddr3_defconfig
index bc76996..28d921e 100644
--- a/configs/ls1043aqds_nor_ddr3_defconfig
+++ b/configs/ls1043aqds_nor_ddr3_defconfig
@@ -6,3 +6,4 @@
 CONFIG_DM=y
 CONFIG_SPI_FLASH=y
 CONFIG_DM_SPI=y
+CONFIG_OF_LIBFDT=y