scsi: pm8001: Fix abort all task initialization

scsi: pm8001: Fix abort all task initialization

In pm80xx_send_abort_all(), the n_elem field of the ccb used is not
initialized to 0. This missing initialization sometimes lead to the task
completion path seeing the ccb with a non-zero n_elem resulting in the
execution of invalid dma_unmap_sg() calls in pm8001_ccb_task_free(),
causing a crash such as:

[  197.676341] RIP: 0010:iommu_dma_unmap_sg+0x6d/0x280
[  197.700204] RSP: 0018:ffff889bbcf89c88 EFLAGS: 00010012
[  197.705485] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff83d0bda0
[  197.712687] RDX: 0000000000000002 RSI: 0000000000000000 RDI: ffff88810dffc0d0
[  197.719887] RBP: 0000000000000000 R08: 0000000000000000 R09: ffff8881c790098b
[  197.727089] R10: ffffed1038f20131 R11: 0000000000000001 R12: 0000000000000000
[  197.734296] R13: ffff88810dffc0d0 R14: 0000000000000010 R15: 0000000000000000
[  197.741493] FS:  0000000000000000(0000) GS:ffff889bbcf80000(0000) knlGS:0000000000000000
[  197.749659] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  197.755459] CR2: 00007f16c1b42734 CR3: 0000000004814000 CR4: 0000000000350ee0
[  197.762656] Call Trace:
[  197.765127]  <IRQ>
[  197.767162]  pm8001_ccb_task_free+0x5f1/0x820 [pm80xx]
[  197.772364]  ? do_raw_spin_unlock+0x54/0x220
[  197.776680]  pm8001_mpi_task_abort_resp+0x2ce/0x4f0 [pm80xx]
[  197.782406]  process_oq+0xe85/0x7890 [pm80xx]
[  197.786817]  ? lock_acquire+0x194/0x490
[  197.790697]  ? handle_irq_event+0x10e/0x1b0
[  197.794920]  ? mpi_sata_completion+0x2d70/0x2d70 [pm80xx]
[  197.800378]  ? __wake_up_bit+0x100/0x100
[  197.804340]  ? lock_is_held_type+0x98/0x110
[  197.808565]  pm80xx_chip_isr+0x94/0x130 [pm80xx]
[  197.813243]  tasklet_action_common.constprop.0+0x24b/0x2f0
[  197.818785]  __do_softirq+0x1b5/0x82d
[  197.822485]  ? do_raw_spin_unlock+0x54/0x220
[  197.826799]  __irq_exit_rcu+0x17e/0x1e0
[  197.830678]  irq_exit_rcu+0xa/0x20
[  197.834114]  common_interrupt+0x78/0x90
[  197.840051]  </IRQ>
[  197.844236]  <TASK>
[  197.848397]  asm_common_interrupt+0x1e/0x40

Avoid this issue by always initializing the ccb n_elem field to 0 in
pm8001_send_abort_all(), pm8001_send_read_log() and
pm80xx_send_abort_all().

Link: https://lore.kernel.org/r/20220220031810.738362-17-damien.lemoal@opensource.wdc.com
Fixes: 39e195660e17 ("[SCSI] pm80xx: NCQ error handling changes")
Reviewed-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>