drbd: Replace vnr_to_mdev() with conn_peer_device()

The new function returns a peer device, which allows us to eliminate a few
instances of first_peer_device().
Signed-off-by: Andreas Gruenbacher <agruen@linbit.com>
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>

drivers/block/drbd/drbd_int.h

@@ -856,14 +856,6 @@ static inline unsigned int device_to_minor(struct drbd_device *device)
 	return device->minor;
 }
 
-static inline struct drbd_device *vnr_to_device(struct drbd_connection *connection, int vnr)
-{
-	struct drbd_peer_device *peer_device;
-
-	peer_device = idr_find(&connection->peer_devices, vnr);
-	return peer_device ? peer_device->device : NULL;
-}
-
 /*
  * function declarations
  *************************/