The recent commit 
916c5e1413be ("hv/netvsc: fix handling of fallback
to single queue mode") tried to fix the fallback behavior to a single
queue mode, but it changed the function to return zero incorrectly,
while the function should return an object pointer.  Eventually this
leads to a NULL dereference at the callers that expect non-NULL
value.
Fix it by returning the proper net_device object.
Fixes: 916c5e1413be ("hv/netvsc: fix handling of fallback to single queue mode")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
        /* setting up multiple channels failed */
        net_device->max_chn = 1;
        net_device->num_chn = 1;
-       return 0;
+       return net_device;
 
 err_dev_remv:
        rndis_filter_device_remove(dev, net_device);