virtio_mmio: fix one typo

fix the typo 'there is are' to 'there are'.

Signed-off-by: Xianting Tian <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Michael S. Tsirkin <[e-mail]>

drivers/virtio/virtio_mmio.c

···
 	/* 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");