* nvqs: the number of virtqueues to find
* vqs: on success, includes new virtqueues
* callbacks: array of callbacks, for each virtqueue
+ * include a NULL entry for vqs that do not need a callback
* names: array of virtqueue names (mainly for debugging)
+ * include a NULL entry for vqs unused by driver
* Returns 0 on success or error status
* @del_vqs: free virtqueues found by find_vqs().
* @get_features: get the array of feature bits for this device.