scsi: lpfc: Return NULL rather than a plain 0 integer

Function lpfc_sli4_perform_vport_cvl() returns a pointer to struct
lpfc_nodelist so returning a plain 0 integer isn't good practice.  Fix this
by returning a NULL instead.

Link: https://lore.kernel.org/r/20210925224113.183040-1-colin.king@canonical.comSigned-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_init.c

@@ -6564,7 +6564,7 @@ lpfc_sli4_perform_vport_cvl(struct lpfc_vport *vport)
 		/* Cannot find existing Fabric ndlp, so allocate a new one */
 		ndlp = lpfc_nlp_init(vport, Fabric_DID);
 		if (!ndlp)
-			return 0;
+			return NULL;
 		/* Set the node type */
 		ndlp->nlp_type |= NLP_FABRIC;
 		/* Put ndlp onto node list */