powerpc: mpc85xx: Add device tree support option for PBL boot image

The current Makefile always use u-boot.bin to generate
PBL boot image (u-boot.pbl), this patch changes it to
use u-boot-with-dtb.bin to support device tree when
CONFIG_OF_SEPARATE is enabled.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/Makefile b/Makefile
index 3b0864a..adb2b9a 100644
--- a/Makefile
+++ b/Makefile
@@ -1256,8 +1256,14 @@
 MKIMAGEFLAGS_u-boot.pbl = -n $(srctree)/$(CONFIG_SYS_FSL_PBL_RCW:"%"=%) \
 		-R $(srctree)/$(CONFIG_SYS_FSL_PBL_PBI:"%"=%) -T pblimage
 
+ifeq ($(CONFIG_MPC85xx)$(CONFIG_OF_SEPARATE),yy)
+UBOOT_BIN := u-boot-with-dtb.bin
+else
+UBOOT_BIN := u-boot.bin
+endif
+
 u-boot-dtb.img u-boot.img u-boot.kwb u-boot.pbl u-boot-ivt.img: \
-		$(if $(CONFIG_SPL_LOAD_FIT),u-boot-nodtb.bin dts/dt.dtb,u-boot.bin) FORCE
+		$(if $(CONFIG_SPL_LOAD_FIT),u-boot-nodtb.bin dts/dt.dtb,$(UBOOT_BIN)) FORCE
 	$(call if_changed,mkimage)
 	$(BOARD_SIZE_CHECK)