s390/dasd,zfcp: fix gcc 8 stringop-truncation warnings

ccw "busid" should always be NUL-terminated, as evident from e.g.
get_ccwdev_by_busid doing "return (strcmp(bus_id, dev_name(dev)) == 0)".

Replace all strncpy initializing busid with strlcpy. This fixes the
following gcc 8 warnings:

drivers/s390/scsi/zfcp_aux.c:104:2: warning: 'strncpy' specified bound 20
equals destination size [-Wstringop-truncation]
  strncpy(busid, token, ZFCP_BUS_ID_SIZE);

drivers/s390/block/dasd_eer.c:316:2: warning: 'strncpy' specified bound 10
equals destination size [-Wstringop-truncation]
  strncpy(header.busid, dev_name(&device->cdev->dev), DASD_EER_BUSID_SIZE);

drivers/s390/block/dasd_eer.c:359:2: warning: 'strncpy' specified bound 10
equals destination size [-Wstringop-truncation]
  strncpy(header.busid, dev_name(&device->cdev->dev), DASD_EER_BUSID_SIZE);

drivers/s390/block/dasd_devmap.c:429:3: warning: 'strncpy' specified bound
20 equals destination size [-Wstringop-truncation]
   strncpy(new->bus_id, bus_id, DASD_BUS_ID_SIZE);
Acked-by: Stefan Haberland <sth@linux.ibm.com>
Acked-by: Steffen Maier <maier@linux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd_devmap.c

@@ -426,7 +426,7 @@ dasd_add_busid(const char *bus_id, int features)
 	if (!devmap) {
 		/* This bus_id is new. */
 		new->devindex = dasd_max_devindex++;
-		strncpy(new->bus_id, bus_id, DASD_BUS_ID_SIZE);
+		strlcpy(new->bus_id, bus_id, DASD_BUS_ID_SIZE);
 		new->features = features;
 		new->device = NULL;
 		list_add(&new->list, &dasd_hashlists[hash]);

drivers/s390/block/dasd_eer.c

@@ -313,7 +313,7 @@ static void dasd_eer_write_standard_trigger(struct dasd_device *device,
 	ktime_get_real_ts64(&ts);
 	header.tv_sec = ts.tv_sec;
 	header.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
-	strncpy(header.busid, dev_name(&device->cdev->dev),
+	strlcpy(header.busid, dev_name(&device->cdev->dev),
 		DASD_EER_BUSID_SIZE);
 
 	spin_lock_irqsave(&bufferlock, flags);
@@ -356,7 +356,7 @@ static void dasd_eer_write_snss_trigger(struct dasd_device *device,
 	ktime_get_real_ts64(&ts);
 	header.tv_sec = ts.tv_sec;
 	header.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
-	strncpy(header.busid, dev_name(&device->cdev->dev),
+	strlcpy(header.busid, dev_name(&device->cdev->dev),
 		DASD_EER_BUSID_SIZE);
 
 	spin_lock_irqsave(&bufferlock, flags);

drivers/s390/scsi/zfcp_aux.c

@@ -101,7 +101,7 @@ static void __init zfcp_init_device_setup(char *devstr)
 	token = strsep(&str, ",");
 	if (!token || strlen(token) >= ZFCP_BUS_ID_SIZE)
 		goto err_out;
-	strncpy(busid, token, ZFCP_BUS_ID_SIZE);
+	strlcpy(busid, token, ZFCP_BUS_ID_SIZE);
 
 	token = strsep(&str, ",");
 	if (!token || kstrtoull(token, 0, (unsigned long long *) &wwpn))