i40e: Fix kernel crash during module removal

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

i40e: Fix kernel crash during module removal

The driver incorrectly frees client instance and subsequent
i40e module removal leads to kernel crash.

Reproducer:
1. Do ethtool offline test followed immediately by another one
host# ethtool -t eth0 offline; ethtool -t eth0 offline
2. Remove recursively irdma module that also removes i40e module
host# modprobe -r irdma

Result:
[ 8675.035651] i40e 0000:3d:00.0 eno1: offline testing starting
[ 8675.193774] i40e 0000:3d:00.0 eno1: testing finished
[ 8675.201316] i40e 0000:3d:00.0 eno1: offline testing starting
[ 8675.358921] i40e 0000:3d:00.0 eno1: testing finished
[ 8675.496921] i40e 0000:3d:00.0: IRDMA hardware initialization FAILED init_state=2 status=-110
[ 8686.188955] i40e 0000:3d:00.1: i40e_ptp_stop: removed PHC on eno2
[ 8686.943890] i40e 0000:3d:00.1: Deleted LAN device PF1 bus=0x3d dev=0x00 func=0x01
[ 8686.952669] i40e 0000:3d:00.0: i40e_ptp_stop: removed PHC on eno1
[ 8687.761787] BUG: kernel NULL pointer dereference, address: 0000000000000030
[ 8687.768755] #PF: supervisor read access in kernel mode
[ 8687.773895] #PF: error_code(0x0000) - not-present page
[ 8687.779034] PGD 0 P4D 0
[ 8687.781575] Oops: 0000 [#1] PREEMPT SMP NOPTI
[ 8687.785935] CPU: 51 PID: 172891 Comm: rmmod Kdump: loaded Tainted: G W I 5.19.0+ #2
[ 8687.794800] Hardware name: Intel Corporation S2600WFD/S2600WFD, BIOS SE5C620.86B.0X.02.0001.051420190324 05/14/2019
[ 8687.805222] RIP: 0010:i40e_lan_del_device+0x13/0xb0 [i40e]
[ 8687.810719] Code: d4 84 c0 0f 84 b8 25 01 00 e9 9c 25 01 00 41 bc f4 ff ff ff eb 91 90 0f 1f 44 00 00 41 54 55 53 48 8b 87 58 08 00 00 48 89 fb <48> 8b 68 30 48 89 ef e8 21 8a 0f d5 48 89 ef e8 a9 78 0f d5 48 8b
[ 8687.829462] RSP: 0018:ffffa604072efce0 EFLAGS: 00010202
[ 8687.834689] RAX: 0000000000000000 RBX: ffff8f43833b2000 RCX: 0000000000000000
[ 8687.841821] RDX: 0000000000000000 RSI: ffff8f4b0545b298 RDI: ffff8f43833b2000
[ 8687.848955] RBP: ffff8f43833b2000 R08: 0000000000000001 R09: 0000000000000000
[ 8687.856086] R10: 0000000000000000 R11: 000ffffffffff000 R12: ffff8f43833b2ef0
[ 8687.863218] R13: ffff8f43833b2ef0 R14: ffff915103966000 R15: ffff8f43833b2008
[ 8687.870342] FS: 00007f79501c3740(0000) GS:ffff8f4adffc0000(0000) knlGS:0000000000000000
[ 8687.878427] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 8687.884174] CR2: 0000000000000030 CR3: 000000014276e004 CR4: 00000000007706e0
[ 8687.891306] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 8687.898441] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 8687.905572] PKRU: 55555554
[ 8687.908286] Call Trace:
[ 8687.910737] <TASK>
[ 8687.912843] i40e_remove+0x2c0/0x330 [i40e]
[ 8687.917040] pci_device_remove+0x33/0xa0
[ 8687.920962] device_release_driver_internal+0x1aa/0x230
[ 8687.926188] driver_detach+0x44/0x90
[ 8687.929770] bus_remove_driver+0x55/0xe0
[ 8687.933693] pci_unregister_driver+0x2a/0xb0
[ 8687.937967] i40e_exit_module+0xc/0xf48 [i40e]

Two offline tests cause IRDMA driver failure (ETIMEDOUT) and this
failure is indicated back to i40e_client_subtask() that calls
i40e_client_del_instance() to free client instance referenced
by pf->cinst and sets this pointer to NULL. During the module
removal i40e_remove() calls i40e_lan_del_device() that dereferences
pf->cinst that is NULL -> crash.
Do not remove client instance when client open callbacks fails and
just clear __I40E_CLIENT_INSTANCE_OPENED bit. The driver also needs
to take care about this situation (when netdev is up and client
is NOT opened) in i40e_notify_client_of_netdev_close() and
calls client close callback only when __I40E_CLIENT_INSTANCE_OPENED
is set.