RDMA: Introduce and use rdma_device_to_ibdev()

Introduce and use rdma_device_to_ibdev() API for those drivers which are
registering one sysfs group and also use in ib_core.

In subsequent patch, device->provider_ibdev one-to-one mapping is no
longer holds true during accessing sysfs entries.
Therefore, introduce an API rdma_device_to_ibdev() that provides such
information.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/sw/rxe/rxe_verbs.c

@@ -1129,8 +1129,8 @@ static int rxe_detach_mcast(struct ib_qp *ibqp, union ib_gid *mgid, u16 mlid)
 static ssize_t parent_show(struct device *device,
 			   struct device_attribute *attr, char *buf)
 {
-	struct rxe_dev *rxe = container_of(device, struct rxe_dev,
-					   ib_dev.dev);
+	struct rxe_dev *rxe =
+		rdma_device_to_drv_device(device, struct rxe_dev, ib_dev);
 
 	return snprintf(buf, 16, "%s\n", rxe_parent_name(rxe, 1));
 }