Avoid extra @FixedSize error.

Here, an error message was emitted for every field if it was emitted on
any previous field.

Bug: N/A
Test: atest aidl_unittests
Change-Id: I2dd7d9641553c212aa24b349cae233c7226806bf
diff --git a/aidl_unittest.cpp b/aidl_unittest.cpp
index 04303c8..0f2f7e6 100644
--- a/aidl_unittest.cpp
+++ b/aidl_unittest.cpp
@@ -2181,6 +2181,7 @@
                                "  ParcelFileDescriptor d;"
                                "  IBinder e;"
                                "  List<String> f;"
+                               "  int isFixedSize;"
                                "}");
   io_delegate_.SetFileContents("Bar.aidl", "parcelable Bar { int a; }");
   Options options =