virtio_mmio: fix one typo

fix the typo 'there is are' to 'there are'.
Signed-off-by: Xianting Tian <xianting_tian@126.com>
Link: https://lore.kernel.org/r/1612615619-8128-1-git-send-email-xianting_tian@126.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio_mmio.c

@@ -126,7 +126,7 @@ static int vm_finalize_features(struct virtio_device *vdev)
 	/* Give virtio_ring a chance to accept features. */
 	vring_transport_features(vdev);
 
-	/* Make sure there is are no mixed devices */
+	/* Make sure there are no mixed devices */
 	if (vm_dev->version == 2 &&
 			!__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
 		dev_err(&vdev->dev, "New virtio-mmio devices (version 2) must provide VIRTIO_F_VERSION_1 feature!\n");