scsi: lpfc: Fix scheduling call while in softirq context in lpfc_unreg_rpi

scsi: lpfc: Fix scheduling call while in softirq context in lpfc_unreg_rpi

The following call trace was seen during HBA reset testing:

BUG: scheduling while atomic: swapper/2/0/0x10000100
...
Call Trace:
dump_stack+0x19/0x1b
__schedule_bug+0x64/0x72
__schedule+0x782/0x840
__cond_resched+0x26/0x30
_cond_resched+0x3a/0x50
mempool_alloc+0xa0/0x170
lpfc_unreg_rpi+0x151/0x630 [lpfc]
lpfc_sli_abts_recover_port+0x171/0x190 [lpfc]
lpfc_sli4_abts_err_handler+0xb2/0x1f0 [lpfc]
lpfc_sli4_io_xri_aborted+0x256/0x300 [lpfc]
lpfc_sli4_sp_handle_abort_xri_wcqe.isra.51+0xa3/0x190 [lpfc]
lpfc_sli4_fp_handle_cqe+0x89/0x4d0 [lpfc]
__lpfc_sli4_process_cq+0xdb/0x2e0 [lpfc]
__lpfc_sli4_hba_process_cq+0x41/0x100 [lpfc]
lpfc_cq_poll_hdler+0x1a/0x30 [lpfc]
irq_poll_softirq+0xc7/0x100
__do_softirq+0xf5/0x280
call_softirq+0x1c/0x30
do_softirq+0x65/0xa0
irq_exit+0x105/0x110
do_IRQ+0x56/0xf0
common_interrupt+0x16a/0x16a

With the conversion to blk_io_poll for better interrupt latency in normal
cases, it introduced this code path, executed when I/O aborts or logouts
are seen, which attempts to allocate memory for a mailbox command to be
issued.  The allocation is GFP_KERNEL, thus it could attempt to sleep.

Fix by creating a work element that performs the event handling for the
remote port. This will have the mailbox commands and other items performed
in the work element, not the irq. A much better method as the "irq" routine
does not stall while performing all this deep handling code.

Ensure that allocation failures are handled and send LOGO on failure.

Additionally, enlarge the mailbox memory pool to reduce the possibility of
additional allocation in this path.

Link: https://lore.kernel.org/r/20201020202719.54726-3-james.smart@broadcom.com
Fixes: 317aeb83c92b ("scsi: lpfc: Add blk_io_poll support for latency improvment")
Cc: <stable@vger.kernel.org> # v5.9+
Co-developed-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>