virtio_config: fix virtio_cread_bytes

virtio_cread_bytes is implemented incorrectly in case length happens to
be 2,4 or 8 bytes: transports and devices will assume it's an integer
value that has to be converted to LE format.

Let's just do multiple 1-byte reads: this also makes life easier
for transports who only need to implement 1,2,4 and 8 byte reads.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

include/linux/virtio_config.h

@@ -305,7 +305,10 @@ static inline void virtio_cread_bytes(struct virtio_device *vdev,
 				      unsigned int offset,
 				      void *buf, size_t len)
 {
-	vdev->config->get(vdev, offset, buf, len);
+	int i;
+
+	for (i = 0; i < len; i++)
+		vdev->config->get(vdev, offset + i, buf + i, 1);
 }
 
 static inline void virtio_cwrite8(struct virtio_device *vdev,