Add u-boot-pad.bin target to the Makefile

Samsung's S3C24XX SoCs need this in order to generate a binary image
with a padded SPL concatenated with U-Boot.

Signed-off-by: José Miguel Gonçalves <jose.goncalves@inov.pt>
[scottwood@freescale.com: fixed prereq of u-boot.ubl]
Signed-off-by: Scott Wood <scottwood@freescale.com>
--
v2: Removed spl/ prefix from u-boot.ubl prerequisite.

Makefile

@@ -474,14 +474,15 @@ $(obj)u-boot.sha1:	$(obj)u-boot.bin
 $(obj)u-boot.dis:	$(obj)u-boot
 		$(OBJDUMP) -d $< > $@
 
-$(obj)u-boot.ubl:       $(obj)spl/u-boot-spl.bin $(obj)u-boot.bin
+$(obj)u-boot-pad.bin:       $(obj)spl/u-boot-spl.bin $(obj)u-boot.bin
 		$(OBJCOPY) ${OBJCFLAGS} --pad-to=$(PAD_TO) -O binary $(obj)spl/u-boot-spl $(obj)spl/u-boot-spl-pad.bin
-		cat $(obj)spl/u-boot-spl-pad.bin $(obj)u-boot.bin > $(obj)u-boot-ubl.bin
-		$(obj)tools/mkimage -n $(UBL_CONFIG) -T ublimage \
-		-e $(CONFIG_SYS_TEXT_BASE) -d $(obj)u-boot-ubl.bin $(obj)u-boot.ubl
-		rm $(obj)u-boot-ubl.bin
+		cat $(obj)spl/u-boot-spl-pad.bin $(obj)u-boot.bin > $(obj)u-boot-pad.bin
 		rm $(obj)spl/u-boot-spl-pad.bin
 
+$(obj)u-boot.ubl:       $(obj)u-boot-pad.bin
+		$(obj)tools/mkimage -n $(UBL_CONFIG) -T ublimage \
+		-e $(CONFIG_SYS_TEXT_BASE) -d $(obj)u-boot-pad.bin $(obj)u-boot.ubl
+
 $(obj)u-boot.ais:       $(obj)spl/u-boot-spl.bin $(obj)u-boot.img
 		$(obj)tools/mkimage -s -n $(if $(CONFIG_AIS_CONFIG_FILE),$(CONFIG_AIS_CONFIG_FILE),"/dev/null") \
 			-T aisimage \