reset num unbuffered writes

src/processor/memory/rom.rs

@@ -81,6 +81,7 @@ impl MaybeBufferedSram {
             writer.seek(SeekFrom::Start(0)).unwrap();
             writer.set_len(self.buf.len() as u64).unwrap();
             writer.write_all(&self.buf).unwrap();
+            self.unbuffered_writes = 0;
         }
     }
 }