spl: Add option SPL_PAYLOAD

Some legacy boards use RAW image for SPL boot. Add Kconfig option
SPL_PAYLOAD to set alternative image.

Signed-off-by: York Sun <york.sun@nxp.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

Makefile

@@ -1111,8 +1111,8 @@ u-boot.sha1:	u-boot.bin
 u-boot.dis:	u-boot
 		$(OBJDUMP) -d $< > $@
 
-ifdef CONFIG_TPL
-SPL_PAYLOAD := tpl/u-boot-with-tpl.bin
+ifneq ($(CONFIG_SPL_PAYLOAD),)
+SPL_PAYLOAD := $(CONFIG_SPL_PAYLOAD:"%"=%)
 else
 SPL_PAYLOAD := u-boot.bin
 endif

common/spl/Kconfig

@@ -553,6 +553,16 @@ config SYS_OS_BASE
 
 endif # SPL_OS_BOOT
 
+config SPL_PAYLOAD
+	string "SPL payload"
+	default "tpl/u-boot-with-tpl.bin" if TPL
+	default "u-boot.bin"
+	help
+	  Payload for SPL boot. For backward compability, default to
+	  u-boot.bin, i.e. RAW image without any header. In case of
+	  TPL, tpl/u-boot-with-tpl.bin. For new boards, suggest to
+	  use u-boot.img.
+
 config SPL_PCI_SUPPORT
 	bool "Support PCI drivers"
 	help