scsi: lpfc: Validate hdwq pointers before dereferencing in reset/errata paths

In the Linux kernel, the following vulnerability has been resolved:

scsi: lpfc: Validate hdwq pointers before dereferencing in reset/errata paths

When the HBA is undergoing a reset or is handling an errata event, NULL ptr

dereference crashes may occur in routines such as

lpfc_sli_flush_io_rings(), lpfc_dev_loss_tmo_callbk(), or

lpfc_abort_handler().

Add NULL ptr checks before dereferencing hdwq pointers that may have been

freed due to operations colliding with a reset or errata event handler.