scsi: qedi: Fix kernel crash during port toggle

scsi: qedi: Fix kernel crash during port toggle

BUG: unable to handle kernel NULL pointer dereference at 0000000000000100

[  985.596918] IP: _raw_spin_lock_bh+0x17/0x30
[  985.601581] PGD 0 P4D 0
[  985.604405] Oops: 0002 [#1] SMP
:
[  985.704533] CPU: 16 PID: 1156 Comm: qedi_thread/16 Not tainted 4.16.0-rc2 #1
[  985.712397] Hardware name: Dell Inc. PowerEdge R730/0599V5, BIOS 2.4.3 01/17/2017
[  985.720747] RIP: 0010:_raw_spin_lock_bh+0x17/0x30
[  985.725996] RSP: 0018:ffffa4b1c43d3e10 EFLAGS: 00010246
[  985.731823] RAX: 0000000000000000 RBX: ffff94a31bd03000 RCX: 0000000000000000
[  985.739783] RDX: 0000000000000001 RSI: ffff94a32fa16938 RDI: 0000000000000100
[  985.747744] RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000a33
[  985.755703] R10: 0000000000000000 R11: ffffa4b1c43d3af0 R12: 0000000000000000
[  985.763662] R13: ffff94a301f40818 R14: 0000000000000000 R15: 000000000000000c
[  985.771622] FS:  0000000000000000(0000) GS:ffff94a32fa00000(0000) knlGS:0000000000000000
[  985.780649] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  985.787057] CR2: 0000000000000100 CR3: 000000067a009006 CR4: 00000000001606e0
[  985.795017] Call Trace:
[  985.797747]  qedi_fp_process_cqes+0x258/0x980 [qedi]
[  985.803294]  qedi_percpu_io_thread+0x10f/0x1b0 [qedi]
[  985.808931]  kthread+0xf5/0x130
[  985.812434]  ? qedi_free_uio+0xd0/0xd0 [qedi]
[  985.817298]  ? kthread_bind+0x10/0x10
[  985.821372]  ? do_syscall_64+0x6e/0x1a0

Signed-off-by: Manish Rangankar <manish.rangankar@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>