kconfig: Move CONFIG_OF_LIBFDT to Kconfig

This patch follows work done by:
"Move CONFIG_OF_LIBFDT to Kconfig"
(sha1: 69e173eb57d1f4848f070c83456096ba5d2ba1b4)

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
[trini: Add xpress* to the patch]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/xpress_spl_defconfig b/configs/xpress_spl_defconfig
index c2b1075..4ac7ef0 100644
--- a/configs/xpress_spl_defconfig
+++ b/configs/xpress_spl_defconfig
@@ -5,3 +5,4 @@
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/imx-common/spl_sd.cfg"
 CONFIG_CMD_DHCP=y
 CONFIG_CMD_PING=y
+CONFIG_OF_LIBFDT=y