tools: mkimage: Add StarFive SPL image support

The StarFive JH7110 base boards require a header to be prefixed to the SPL
binary image. This has previously done with a vendor tool 'spl_tool'
published under a GPL-2-or-later license. Integrate this capability into
mkimage.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Tested-by: Chanho Park <chanho61.park@samsung.com>
Tested-by: Milan P. Stanić <mps@arvanta.net>
diff --git a/boot/image.c b/boot/image.c
index 26f68d4..88b67bc 100644
--- a/boot/image.c
+++ b/boot/image.c
@@ -182,6 +182,7 @@
 	{	IH_TYPE_SUNXI_TOC0, "sunxi_toc0",  "Allwinner TOC0 Boot Image" },
 	{	IH_TYPE_FDT_LEGACY, "fdt_legacy", "legacy Image with Flat Device Tree ", },
 	{	IH_TYPE_RENESAS_SPKG, "spkgimage", "Renesas SPKG Image" },
+	{	IH_TYPE_STARFIVE_SPL, "sfspl", "StarFive SPL Image" },
 	{	-1,		    "",		  "",			},
 };