scsi: lpfc: Fix miss of register read failure check

Coverity flagged missing status check on register read that flags a
poisoned data return value.

Add checking of register read status.

Link: https://lore.kernel.org/r/20190922035906.10977-4-jsmart2021@gmail.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>