scsi: lpfc: avoid double free of resource identifiers

Set variables initialized in lpfc_sli4_alloc_resource_identifiers() to
NULL if an error occurred. Otherwise, lpfc_sli4_driver_resource_unset()
attempts to free the memory again.

Signed-off-by: Roberto Sassu <rsassu@suse.de>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Acked-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>