net/mlx5: Fix steering rules cleanup

In the Linux kernel, the following vulnerability has been resolved:

net/mlx5: Fix steering rules cleanup

vport's mc, uc and multicast rules are not deleted in teardown path when
EEH happens. Since the vport's promisc settings(uc, mc and all) in
firmware are reset after EEH, mlx5 driver will try to delete the above
rules in the initialization path. This cause kernel crash because these
software rules are no longer valid.

Fix by nullifying these rules right after delete to avoid accessing any dangling
pointers.

Call Trace:
__list_del_entry_valid+0xcc/0x100 (unreliable)
tree_put_node+0xf4/0x1b0 [mlx5_core]
tree_remove_node+0x30/0x70 [mlx5_core]
mlx5_del_flow_rules+0x14c/0x1f0 [mlx5_core]
esw_apply_vport_rx_mode+0x10c/0x200 [mlx5_core]
esw_update_vport_rx_mode+0xb4/0x180 [mlx5_core]
esw_vport_change_handle_locked+0x1ec/0x230 [mlx5_core]
esw_enable_vport+0x130/0x260 [mlx5_core]
mlx5_eswitch_enable_sriov+0x2a0/0x2f0 [mlx5_core]
mlx5_device_enable_sriov+0x74/0x440 [mlx5_core]
mlx5_load_one+0x114c/0x1550 [mlx5_core]
mlx5_pci_resume+0x68/0xf0 [mlx5_core]
eeh_report_resume+0x1a4/0x230
eeh_pe_dev_traverse+0x98/0x170
eeh_handle_normal_event+0x3e4/0x640
eeh_handle_event+0x4c/0x370
eeh_event_handler+0x14c/0x210
kthread+0x168/0x1b0
ret_from_kernel_thread+0x5c/0x84