x86: image: Add new image type for x64_64

This is a bit odd in that we are permitted to boot images for either, even
though they are separate architectures.

Signed-off-by: Simon Glass <sjg@chromium.org>

common/image.c

@@ -85,6 +85,7 @@ static const table_entry_t uimage_arch[] = {
 	{	IH_ARCH_SANDBOX,	"sandbox",	"Sandbox",	},
 	{	IH_ARCH_ARM64,		"arm64",	"AArch64",	},
 	{	IH_ARCH_ARC,		"arc",		"ARC",		},
+	{	IH_ARCH_X86_64,		"x86_64",	"AMD x86_64",	},
 	{	-1,			"",		"",		},
 };