scsi: qla4xxx: Prevent a potential error pointer dereference

JIRA: https://issues.redhat.com/browse/RHEL-121669

The qla4xxx_get_ep_fwdb() function is supposed to return NULL on error,
but qla4xxx_ep_connect() returns error pointers.  Propagating the error
pointers will lead to an Oops in the caller, so change the error pointers
to NULL.

Fixes: 1348373 ("[SCSI] qla4xxx: fix flash/ddb support")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/aJwnVKS9tHsw1tEu@stanley.mountain
Reviewed-by: Chris Leech <cleech@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
(cherry picked from commit 9dcf111)
Signed-off-by: Chris Leech <cleech@redhat.com>

Author: cleech

drivers/scsi/qla4xxx/ql4_os.c

@@ -6606,6 +6606,8 @@ static struct iscsi_endpoint *qla4xxx_get_ep_fwdb(struct scsi_qla_host *ha,
 
 	ep = qla4xxx_ep_connect(ha->host, (struct sockaddr *)dst_addr, 0);
 	vfree(dst_addr);
+	if (IS_ERR(ep))
+		return NULL;
 	return ep;
 }