Implement can_recv in terms of poll_receive.

src/device/net/dev.rs

@@ -67,7 +67,7 @@ impl<H: Hal, T: Transport, const QUEUE_SIZE: usize> VirtIONet<H, T, QUEUE_SIZE>
 
     /// Whether can receive packet.
     pub fn can_recv(&self) -> bool {
-        self.inner.can_recv()
+        self.inner.poll_receive().is_some()
     }
 
     /// Receives a [`RxBuffer`] from network. If currently no data, returns an

src/device/net/dev_raw.rs

@@ -210,7 +210,7 @@ impl<H: Hal, T: Transport, const QUEUE_SIZE: usize> VirtIONetRaw<H, T, QUEUE_SIZ
     /// Fetches the token of the next completed reception request from the
     /// used ring and returns it, without removing it from the used ring. If
     /// there are no pending completed requests it returns [`None`].
-    pub fn poll_receive(&mut self) -> Option<u16> {
+    pub fn poll_receive(&self) -> Option<u16> {
         self.recv_queue.peek_used()
     }