x86: Add an fdtmap and image-header

Add these entries to the ROM so that we can list the contents of an image
with 'binman ls'. The image-header is not essential but does speed up
access.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/dts/u-boot.dtsi

@@ -124,6 +124,8 @@
 		filename = CONFIG_FSP_FILE_S;
 	};
 #endif
+	fdtmap {
+	};
 #ifdef CONFIG_HAVE_CMC
 	intel-cmc {
 		filename = CONFIG_CMC_FILE;
@@ -169,5 +171,8 @@
 		offset = <CONFIG_RESET_VEC_LOC>;
 	};
 #endif
+	image-header {
+		location = "end";
+	};
 };
 #endif