hw/audio/virtio-snd: Remove unused assignment

Coverity reported:

  >>>     CID 1542933:  Code maintainability issues  (UNUSED_VALUE)
  >>>     CID 1542934:  Code maintainability issues  (UNUSED_VALUE)
  >>>     Assigning value "NULL" to "stream" here, but that stored
          value is overwritten before it can be used.

Simply remove the unused assignments.

Resolves: Coverity CID 1542933
Resolves: Coverity CID 1542934
Fixes: 731655f ("virtio-snd: rewrite invalid tx/rx message handling")
Fixes: 20cd0c8 ("virtio-snd: rewrite invalid tx/rx message handling" in stable-8.2)
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Message-Id: <20240410053712.34747-1-philmd@linaro.org>
(cherry picked from commit dcb0a1a)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/audio/virtio-snd.c

@@ -885,7 +885,9 @@ static void virtio_snd_handle_tx_xfer(VirtIODevice *vdev, VirtQueue *vq)
     }
     trace_virtio_snd_handle_tx_xfer();
 
-    for (VirtIOSoundPCMStream *stream = NULL;; stream = NULL) {
+    for (;;) {
+        VirtIOSoundPCMStream *stream;
+
         elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
         if (!elem) {
             break;
@@ -964,7 +966,9 @@ static void virtio_snd_handle_rx_xfer(VirtIODevice *vdev, VirtQueue *vq)
     }
     trace_virtio_snd_handle_rx_xfer();
 
-    for (VirtIOSoundPCMStream *stream = NULL;; stream = NULL) {
+    for (;;) {
+        VirtIOSoundPCMStream *stream;
+
         elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
         if (!elem) {
             break;