[S390] dasd: check_characteristics cleanup

Fix a broken memset (sizeof pointer vs sizeof the underlying
structure) by cleaning up the involved functions.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/block/dasd_fba.c b/drivers/s390/block/dasd_fba.c
index 8912358..8c3c8ffb 100644
--- a/drivers/s390/block/dasd_fba.c
+++ b/drivers/s390/block/dasd_fba.c
@@ -122,20 +122,20 @@
 	struct dasd_block *block;
 	struct dasd_fba_private *private;
 	struct ccw_device *cdev = device->cdev;
-	void *rdc_data;
 	int rc;
 
 	private = (struct dasd_fba_private *) device->private;
-	if (private == NULL) {
-		private = kzalloc(sizeof(struct dasd_fba_private),
-				  GFP_KERNEL | GFP_DMA);
-		if (private == NULL) {
+	if (!private) {
+		private = kzalloc(sizeof(*private), GFP_KERNEL | GFP_DMA);
+		if (!private) {
 			dev_warn(&device->cdev->dev,
 				 "Allocating memory for private DASD "
 				 "data failed\n");
 			return -ENOMEM;
 		}
 		device->private = (void *) private;
+	} else {
+		memset(private, 0, sizeof(*private));
 	}
 	block = dasd_alloc_block();
 	if (IS_ERR(block)) {
@@ -150,8 +150,8 @@
 	block->base = device;
 
 	/* Read Device Characteristics */
-	rdc_data = (void *) &(private->rdc_data);
-	rc = dasd_generic_read_dev_chars(device, "FBA ", &rdc_data, 32);
+	rc = dasd_generic_read_dev_chars(device, "FBA ", &private->rdc_data,
+					 32);
 	if (rc) {
 		DBF_EVENT(DBF_WARNING, "Read device characteristics returned "
 			  "error %d for device: %s",