qla2xxx: Allow vref count to timeout on vport delete.

qla2xxx: Allow vref count to timeout on vport delete.

This commit fixed a panic could be triggered with following steps:
1.create vhba
  #virsh nodedev-create  vhba.xml
2.destroy vhba
  #virsh nodedev-destroy scsi_host9

Content of file vhba.xml:

<device>
     <parent>scsi_host7</parent>
     <capability type='scsi_host'>
       <capability type='fc_host'>
       </capability>
     </capability>
</device>

Call trace of panic:

[  207.683754] BUG: unable to handle kernel NULL pointer dereference at 0000000000000410
[  207.683805] IP: [<ffffffffa0221d0f>] qla24xx_vport_delete+0xdf/0x180 [qla2xxx]
[  207.683850] PGD 0
[  207.683863] Oops: 0000 [#1] SMP
[  207.684391] CPU: 0 PID: 2029 Comm: libvirtd Not tainted 4.1.12-94.2.1.el7uek.x86_64 #2
[  207.684418] Hardware name: Oracle Corporation ORACLE SERVER X5-2/ASM,MOTHERBOARD,1U, BIOS 30100400 12/26/2016
[  207.684454] task: ffff88026fc31c00 ti: ffff88007278c000 task.ti: ffff88007278c000
[  207.684491] RIP: 0010:[<ffffffffa0221d0f>]  [<ffffffffa0221d0f>] qla24xx_vport_delete+0xdf/0x180 [qla2xxx]
[  207.684535] RSP: 0018:ffff88007278fcf8  EFLAGS: 00010202
[  207.684555] RAX: 0000000000000001 RBX: ffff8802729c17f8 RCX: ffffffffa0258e80
[  207.684578] RDX: 0000000000007086 RSI: 0000000000000000 RDI: ffff88026fef0360
[  207.684601] RBP: ffff88007278fd18 R08: 0000000000000001 R09: ffff88027741ad80
[  207.684625] R10: ffffea0009bbbc00 R11: 0000000000000000 R12: ffff88026fef0000
[  207.684649] R13: 0000000000000001 R14: ffff88026fef0360 R15: 0000000000000021
[  207.684673] FS:  00007f24f538d700(0000) GS:ffff880277400000(0000) knlGS:0000000000000000
[  207.684699] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  207.684719] CR2: 0000000000000410 CR3: 00000002731e7000 CR4: 00000000001406f0
[  207.684744] Stack:
[  207.684755]  ffff8802733dd800 ffff8802728fd000 ffff880474d3f000 ffff880474d3f648
[  207.684785]  ffff88007278fd58 ffffffffa000d344 ffff8804714f4000 ffff8802728fd000
[  207.684814]  ffff8802728fd000 ffff8802733dd800 0000000000000021 ffff880474d3f648
[  207.684861] Call Trace:
[  207.684897]  [<ffffffffa000d344>] fc_vport_terminate+0x44/0x150 [scsi_transport_fc]
[  207.684927]  [<ffffffffa000d594>] store_fc_host_vport_delete+0x144/0x180 [scsi_transport_fc]
[  207.684959]  [<ffffffff81489798>] dev_attr_store+0x18/0x30
[  207.684996]  [<ffffffff81294fbd>] sysfs_kf_write+0x3d/0x50
[  207.685017]  [<ffffffff8129446a>] kernfs_fop_write+0x12a/0x180
[  207.685040]  [<ffffffff812129b7>] __vfs_write+0x37/0x120
[  207.685061]  [<ffffffff812158d8>] ? __sb_start_write+0x58/0x110
[  207.685084]  [<ffffffff812c1743>] ? security_file_permission+0x23/0xa0
[  207.685107]  [<ffffffff812130f9>] vfs_write+0xa9/0x1b0
[  207.685128]  [<ffffffff81736c16>] ? mutex_lock+0x16/0x37
[  207.685147]  [<ffffffff81213fe5>] SyS_write+0x55/0xd0
[  207.685179]  [<ffffffff81738c6e>] system_call_fastpath+0x12/0x71
[  207.685200] Code: 07 00 00 01 0f b7 83 b0 01 00 00 f0 49 0f b3 84 24 30 07 00 00 4c 89 f7 e8 5f 4d 51 e1 48 8b b3 b8 01 00 00 0f b7 83 b0 01 00 00 <66> 39 86 10 04 00 00 74 68 45 0f b7 c5 48 89 de 31 c0 48 c7 c1
[  207.686827] RIP  [<ffffffffa0221d0f>] qla24xx_vport_delete+0xdf/0x180 [qla2xxx]
[  207.687634]  RSP <ffff88007278fcf8>
[  207.688391] CR2: 0000000000000410

Cc: <stable@vger.kernel.org>
Signed-off-by: Joe Carnuccio <joe.carnuccio@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
(cherry picked from commit c4a9b538ab2a109c5f9798bea1f8f4bf93aadfb9)

Orabug: 26021151

Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
Conflicts:
	drivers/scsi/qla2xxx/qla_attr.c
	drivers/scsi/qla2xxx/qla_def.h
	drivers/scsi/qla2xxx/qla_os.c