net/mlx5e: Fix cleanup null-ptr deref on encap lock

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

net/mlx5e: Fix cleanup null-ptr deref on encap lock

During module is unloaded while a peer tc flow is still offloaded,
first the peer uplink rep profile is changed to a nic profile, and so
neigh encap lock is destroyed. Next during unload, the VF reps netdevs
are unregistered which causes the original non-peer tc flow to be deleted,
which deletes the peer flow. The peer flow deletion detaches the encap
entry and try to take the already destroyed encap lock, causing the
below trace.

Fix this by clearing peer flows during tc eswitch cleanup
(mlx5e_tc_esw_cleanup()).

Relevant trace:
[ 4316.837128] BUG: kernel NULL pointer dereference, address: 00000000000001d8
[ 4316.842239] RIP: 0010:__mutex_lock+0xb5/0xc40
[ 4316.851897] Call Trace:
[ 4316.852481] <TASK>
[ 4316.857214] mlx5e_rep_neigh_entry_release+0x93/0x790 [mlx5_core]
[ 4316.858258] mlx5e_rep_encap_entry_detach+0xa7/0xf0 [mlx5_core]
[ 4316.859134] mlx5e_encap_dealloc+0xa3/0xf0 [mlx5_core]
[ 4316.859867] clean_encap_dests.part.0+0x5c/0xe0 [mlx5_core]
[ 4316.860605] mlx5e_tc_del_fdb_flow+0x32a/0x810 [mlx5_core]
[ 4316.862609] __mlx5e_tc_del_fdb_peer_flow+0x1a2/0x250 [mlx5_core]
[ 4316.863394] mlx5e_tc_del_flow+0x(/0x630 [mlx5_core]
[ 4316.864090] mlx5e_flow_put+0x5f/0x100 [mlx5_core]
[ 4316.864771] mlx5e_delete_flower+0x4de/0xa40 [mlx5_core]
[ 4316.865486] tc_setup_cb_reoffload+0x20/0x80
[ 4316.865905] fl_reoffload+0x47c/0x510 [cls_flower]
[ 4316.869181] tcf_block_playback_offloads+0x91/0x1d0
[ 4316.869649] tcf_block_unbind+0xe7/0x1b0
[ 4316.870049] tcf_block_offload_cmd.isra.0+0x1ee/0x270
[ 4316.879266] tcf_block_offload_unbind+0x61/0xa0
[ 4316.879711] __tcf_block_put+0xa4/0x310