[SCSI] initialize shost_data to zero

It's better to initialize host->shost_data to zero like
target->starget_data and device->sdev_data.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/hosts.c

@@ -220,7 +220,7 @@ int scsi_add_host(struct Scsi_Host *shost, struct device *dev)
 	get_device(&shost->shost_gendev);
 
 	if (shost->transportt->host_size &&
-	    (shost->shost_data = kmalloc(shost->transportt->host_size,
+	    (shost->shost_data = kzalloc(shost->transportt->host_size,
 					 GFP_KERNEL)) == NULL)
 		goto out_del_classdev;