tools: binman: Add missing filenames for various x86 rom tests

With recent changes, some x86-specific rom tests of binman fail to
run. Fix it by adding missing filenames in corresponding entries.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/test/31_x86-rom-me.dts b/tools/binman/test/31_x86-rom-me.dts
index b484ab3..ee3dac8 100644
--- a/tools/binman/test/31_x86-rom-me.dts
+++ b/tools/binman/test/31_x86-rom-me.dts
@@ -9,9 +9,11 @@
 		end-at-4gb;
 		size = <0x800000>;
 		intel-descriptor {
+			filename = "descriptor.bin";
 		};
 
 		intel-me {
+			filename = "me.bin";
 			pos-unset;
 		};
 	};