Always take this timestamp

Author: datdenkikniet

src/dma/tx.rs

@@ -216,7 +216,12 @@ impl TxRingEntry {
             if packet_id.is_some() {
                 extra_flags |= TXDESC_0_TIMESTAMP_ENABLE | TXDESC_0_LS | TXDESC_0_FS;
             }
+
             self.desc_mut().packet_id = packet_id;
+            #[cfg(feature = "ptp")]
+            // Remove old timestamp data when the packet ID is
+            // changed.
+            self.desc_mut().cached_timestamp.take();
 
             extra_flags |= TXDESC_0_IC;