rockchip: spl-boot-order: update dependency to OF_LIBFDT

The fdt interfaces are actuall depends on OF_LIBFDT instead
of OF_CONTROL, some boards may enable OF_CONTROL while disable
OF_LIBFDT.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/mach-rockchip/spl-boot-order.c b/arch/arm/mach-rockchip/spl-boot-order.c
index 0e485de..c19c285 100644
--- a/arch/arm/mach-rockchip/spl-boot-order.c
+++ b/arch/arm/mach-rockchip/spl-boot-order.c
@@ -8,7 +8,7 @@
 #include <mmc.h>
 #include <spl.h>
 
-#if CONFIG_IS_ENABLED(OF_CONTROL)
+#if CONFIG_IS_ENABLED(OF_LIBFDT)
 /**
  * spl_node_to_boot_device() - maps from a DT-node to a SPL boot device
  * @node:	of_offset of the node