scsi: qla2xxx: Fix kernel crash after disconnecting NVMe devices

scsi: qla2xxx: Fix kernel crash after disconnecting NVMe devices

BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: [<ffffffffc050d10c>] qla_nvme_unregister_remote_port+0x6c/0xf0 [qla2xxx]
PGD 800000084cf41067 PUD 84d288067 PMD 0
Oops: 0000 [#1] SMP
Call Trace:
 [<ffffffff98abcfdf>] process_one_work+0x17f/0x440
 [<ffffffff98abdca6>] worker_thread+0x126/0x3c0
 [<ffffffff98abdb80>] ? manage_workers.isra.26+0x2a0/0x2a0
 [<ffffffff98ac4f81>] kthread+0xd1/0xe0
 [<ffffffff98ac4eb0>] ? insert_kthread_work+0x40/0x40
 [<ffffffff9918ad37>] ret_from_fork_nospec_begin+0x21/0x21
 [<ffffffff98ac4eb0>] ? insert_kthread_work+0x40/0x40
RIP  [<ffffffffc050d10c>] qla_nvme_unregister_remote_port+0x6c/0xf0 [qla2xxx]

The crash is due to a bad entry in the nvme_rport_list. This list is not
protected, and when a remoteport_delete callback is called, driver
traverses the list and crashes.

Actually, the list could be removed and driver could traverse the main
fcport list instead. Fix does exactly that.

Signed-off-by: Arun Easi <aeasi@marvell.com>
Signed-off-by: Himanshu Madhani <hmadhani@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>