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/omap5_uevm_defconfig b/configs/omap5_uevm_defconfig
index ba5d9ca..cdd80cc 100644
--- a/configs/omap5_uevm_defconfig
+++ b/configs/omap5_uevm_defconfig
@@ -7,3 +7,4 @@
 CONFIG_CMD_GPIO=y
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_SYS_NS16550=y
+CONFIG_OF_LIBFDT=y