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/42_intel-fsp.dts b/tools/binman/test/42_intel-fsp.dts
index e0a1e76..8a7c889 100644
--- a/tools/binman/test/42_intel-fsp.dts
+++ b/tools/binman/test/42_intel-fsp.dts
@@ -8,6 +8,7 @@
 		size = <16>;
 
 		intel-fsp {
+			filename = "fsp.bin";
 		};
 	};
 };