spl: Change PAD_TO to CONFIG_SPL_PAD_TO

This was already used by some SPL targets, and allows the pad amount to
be specified by board config headers rather than only in makefile
fragments.

Also supply a pad-to of zero if the variable is undefined.  It works
without this, but this avoids relying on undocumented behavior.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>

Makefile

@@ -485,8 +485,12 @@ $(obj)u-boot.sha1:	$(obj)u-boot.bin
 $(obj)u-boot.dis:	$(obj)u-boot
 		$(OBJDUMP) -d $< > $@
 
+
+
 $(obj)u-boot-with-spl.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
+		$(OBJCOPY) ${OBJCFLAGS} --pad-to=$(or $(CONFIG_SPL_PAD_TO),0) \
+			-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 > $@
 		rm $(obj)spl/u-boot-spl-pad.bin
 

README

@@ -2836,6 +2836,10 @@ FIT uImage format:
 		CONFIG_SPL_LIBGENERIC_SUPPORT
 		Support for lib/libgeneric.o in SPL binary
 
+		CONFIG_SPL_PAD_TO
+		Linker address to which the SPL should be padded before
+		appending the SPL payload.
+
 		CONFIG_SPL_TARGET
 		Final target image containing SPL and payload.  Some SPLs
 		use an arch-specific makefile fragment instead, for

board/ait/cam_enc_4xx/config.mk

@@ -8,7 +8,7 @@
 #
 
 #Provide at least 16MB spacing between us and the Linux Kernel image
-PAD_TO	:= 12320
+CONFIG_SPL_PAD_TO := 12320
 UBL_CONFIG = $(SRCTREE)/board/$(BOARDDIR)/ublimage.cfg
 ifndef CONFIG_SPL_BUILD
 ALL-y += $(obj)u-boot.ubl