message: create limit for the number of supported virtio queues
diff: #define VENDOR_ID 0x1AF4
  #define VIOIF_BUFFER_SIZE 0x2048
  #define MIN(a, b) (a) < (b) ? (a) : (b)
  +#define QUEUE_LIMIT 256
  static struct netif* mynetif = NULL;
  @@ -278,6 +279,11 @@ static int vioif_queue_setup(vioif_t* dev, uint32_t index)
  memset((void*)vring_base, 0x00, total_size);
  vring_init(&vq->vring, num, vring_base, PAGE_SIZE);
  + if (num > QUEUE_LIMIT) {
  + vq->vring.num = num = QUEUE_LIMIT;
  + LOG_INFO("vioif: set queue limit to %u (index %u)\n", vq->vring.num, index);
  + }
  +
  vq->virt_buffer = (uint64_t) page_alloc(num*VIOIF_BUFFER_SIZE, VMA_READ|VMA_WRITE|VMA_CACHEABLE);
  if (BUILTIN_EXPECT(!vq->virt_buffer, 0)) {
  LOG_INFO("Not enough memory to create buffer %u\n", index);
  