scsi: lpfc: Fix crash caused by switch reboot

scsi: lpfc: Fix crash caused by switch reboot

Driver is causing a crash in __lpfc_sli_release_iocbq_s4() when it
dereferences the els_wq which is NULL.

Validate the pring for the els_wq before dereferencing. Reorg the code to
move the pring assignment closer to where it is actually used.

Link: https://lore.kernel.org/r/20210301171821.3427-18-jsmart2021@gmail.com
Co-developed-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>