net/mlx5: E-switch, unload IB representors when unloading ETH representors

IB representors depend on ETH representors, so the IB representors
should not exist without the ETH ones. When unloading the ETH
representors, the corresponding IB representors should be also
unloaded.

The commit 8d159eb2 ("RDMA/mlx5: Use IB set_netdev and get_netdev functions")
introduced the use of the ib_device_set_netdev API in IB
repsresentors. ib_device_set_netdev() increments the refcount of
the representor's netdev when loading an IB representor and
decrements it when unloading.
Without the unloading of the IB representor, the refcount of the
representor's netdev remains greater than 0, preventing it from
being unregistered.
The patch uncovered an underlying bug where the eth representor is
unloaded, without unloading the IB representor.

This issue happened when using multiport E-switch and rebooting,
causing the shutdown to hang when unloading the ETH representor
because the refcount of the representor's netdevice was greater than 0.

Call trace:
unregister_netdevice: waiting for eth3 to become free. Usage count = 2
ref_tracker: eth%d@00000000661d60f7 has 1/1 users at
	ib_device_set_netdev+0x160/0x2d0 [ib_core]
	mlx5_ib_vport_rep_load+0x104/0x3f0 [mlx5_ib]
	mlx5_eswitch_reload_ib_reps+0xfc/0x110 [mlx5_core]
	mlx5_mpesw_work+0x236/0x330 [mlx5_core]
	process_one_work+0x169/0x320
	worker_thread+0x288/0x3a0
	kthread+0xb8/0xe0
	ret_from_fork+0x2d/0x50
	ret_from_fork_asm+0x11/0x20

Fixes: 8d159eb2 ("RDMA/mlx5: Use IB set_netdev and get_netdev functions")
Signed-off-by: Chiara Meiohas <cmeiohas@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20241107183527.676877-2-tariqt@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>