Fix double free problem within qla2xxx driver where
current code prematurely free qla_tgt_cmd while firmware
still has the command.  When firmware release the command
after abort, the code attempt a second free as part of
command completion processing.

When TCM start the free process, NULL pointer was hit.

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WARNING: CPU: 8 PID: 43613 at lib/list_debug.c:62 __list_del_entry+0x82/0xd0()
list_del corruption. next->prev should be ffff88082b5cfb08, but was 6b6b6b6b6b6b6b6b
CPU: 8 PID: 43613 Comm: kworker/8:0 Tainted: GF       W  O 3.13.0-rc3-nab_t10dif+ #6
Hardware name: HP ProLiant DL380p Gen8, BIOS P70 08/20/2012
Workqueue: events cache_reap
000000000000003e ffff88081b2e3c78 ffffffff815a051f 000000000000003e
ffff88081b2e3cc8 ffff88081b2e3cb8 ffffffff8104fc2c 0000000000000000
ffff88082b5cfb00 ffff88081c788d00 ffff88082b5d7200 ffff88082b5d3080
Call Trace:
[<ffffffff815a051f>] dump_stack+0x49/0x62
[<ffffffff8104fc2c>] warn_slowpath_common+0x8c/0xc0
[<ffffffff8104fd16>] warn_slowpath_fmt+0x46/0x50
[<ffffffff812b6592>] __list_del_entry+0x82/0xd0
[<ffffffff8106d48c>] process_one_work+0x12c/0x510
[<ffffffff8106d4d3>] ? process_one_work+0x173/0x510
[<ffffffff8106ebdf>] worker_thread+0x11f/0x3a0
[<ffffffff8106eac0>] ? manage_workers+0x170/0x170
[<ffffffff81074f26>] kthread+0xf6/0x120
[<ffffffff8109f103>] ? __lock_release+0x133/0x1b0
[<ffffffff81074e30>] ? __init_kthread_worker+0x70/0x70
[<ffffffff815aec2c>] ret_from_fork+0x7c/0xb0
[<ffffffff81074e30>] ? __init_kthread_worker+0x70/0x70
---[ end trace dfc05c3f7caf8ebe ]---
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: [<ffffffff8106d391>] process_one_work+0x31/0x510
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Signed-off-by: Quinn Tran <quinn.tran@qlogic.com>
Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: Saurav Kashyap <saurav.kashyap@qlogic.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>