tools: add i.MX8/8X image support

i.MX8/8X bootable image type is container type.
The bootable image, containers a container set which supports two
container. The 1st container is for SECO firmware, the 2nd container
needs to include scfw, m4_0/1 image, ACore images per your requirement.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/common/image.c b/common/image.c
index 4f20128..1c3a772 100644
--- a/common/image.c
+++ b/common/image.c
@@ -139,6 +139,7 @@
 	{	IH_TYPE_KERNEL_NOLOAD, "kernel_noload",  "Kernel Image (no loading done)", },
 	{	IH_TYPE_KWBIMAGE,   "kwbimage",   "Kirkwood Boot Image",},
 	{	IH_TYPE_IMXIMAGE,   "imximage",   "Freescale i.MX Boot Image",},
+	{	IH_TYPE_IMX8IMAGE,  "imx8image",  "NXP i.MX8 Boot Image",},
 	{	IH_TYPE_INVALID,    "invalid",	  "Invalid Image",	},
 	{	IH_TYPE_MULTI,	    "multi",	  "Multi-File Image",	},
 	{	IH_TYPE_OMAPIMAGE,  "omapimage",  "TI OMAP SPL With GP CH",},