spl: Use u-boot.img instead of u-boot.bin

In SD boot, the magic number of u-boot image will be checked.
For LS102xA, u-boot.bin doesn't have the magic number. So use
u-boot.img which includes the magic number instead of u-boot.bin
when producing u-boot-with-spl-pbl.bin.

Signed-off-by: Alison Wang <alison.wang@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>

Makefile

@@ -1005,10 +1005,16 @@ MKIMAGEFLAGS_u-boot-spl.pbl = -n $(srctree)/$(CONFIG_SYS_FSL_PBL_RCW:"%"=%) \
 spl/u-boot-spl.pbl: spl/u-boot-spl.bin FORCE
 	$(call if_changed,mkimage)
 
+ifeq ($(ARCH),arm)
+UBOOT_BINLOAD := u-boot.img
+else
+UBOOT_BINLOAD := u-boot.bin
+endif
+
 OBJCOPYFLAGS_u-boot-with-spl-pbl.bin = -I binary -O binary --pad-to=$(CONFIG_SPL_PAD_TO) \
 			  --gap-fill=0xff
 
-u-boot-with-spl-pbl.bin: spl/u-boot-spl.pbl u-boot.bin FORCE
+u-boot-with-spl-pbl.bin: spl/u-boot-spl.pbl $(UBOOT_BINLOAD) FORCE
 	$(call if_changed,pad_cat)
 
 # PPC4xx needs the SPL at the end of the image, since the reset vector