RDMA/mlx5: Cleanup rep when doing unload

When an IB rep is loaded, netdev for the same vport is saved for later
reference. However, it's not cleaned up when doing unload. For ECPF,
kernel crashes when driver is referring to the already removed netdev.

Following steps lead to a shown call trace:
1. Create n VFs from host PF
2. Distroy the VFs
3. Run "rdma link" from ARM

Call trace:
  mlx5_ib_get_netdev+0x9c/0xe8 [mlx5_ib]
  mlx5_query_port_roce+0x268/0x558 [mlx5_ib]
  mlx5_ib_rep_query_port+0x14/0x34 [mlx5_ib]
  ib_query_port+0x9c/0xfc [ib_core]
  fill_port_info+0x74/0x28c [ib_core]
  nldev_port_get_doit+0x1a8/0x1e8 [ib_core]
  rdma_nl_rcv_msg+0x16c/0x1c0 [ib_core]
  rdma_nl_rcv+0xe8/0x144 [ib_core]
  netlink_unicast+0x184/0x214
  netlink_sendmsg+0x288/0x354
  sock_sendmsg+0x18/0x2c
  __sys_sendto+0xbc/0x138
  __arm64_sys_sendto+0x28/0x34
  el0_svc_common+0xb0/0x100
  el0_svc_handler+0x6c/0x84
  el0_svc+0x8/0xc

Cleanup the rep and netdev reference when unloading IB rep.

Fixes: 26628e2d ("RDMA/mlx5: Move to single device multiport ports in switchdev mode")
Signed-off-by: Bodong Wang <bodong@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>