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>
diff --git a/common/bootm.c b/common/bootm.c
index 81e3261..6b3ea8c 100644
--- a/common/bootm.c
+++ b/common/bootm.c
@@ -167,7 +167,8 @@
 	}
 
 	/* If we have a valid setup.bin, we will use that for entry (x86) */
-	if (images.os.arch == IH_ARCH_I386) {
+	if (images.os.arch == IH_ARCH_I386 ||
+	    images.os.arch == IH_ARCH_X86_64) {
 		ulong len;
 
 		ret = boot_get_setup(&images, IH_ARCH_I386, &images.ep, &len);