s390/dcssblk: fix device size calculation in dcssblk_direct_access()

Since commit dd22f551 "block: Change direct_access calling convention",
the device size calculation in dcssblk_direct_access() is off-by-one.
This results in bdev_direct_access() always returning -ENXIO because the
returned value is not page aligned.

Fix this by adding 1 to the dev_sz calculation.

Fixes: dd22f551 ("block: Change direct_access calling convention")
Cc: <stable@vger.kernel.org> # 4.0+
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dcssblk.c

@@ -892,7 +892,7 @@ dcssblk_direct_access (struct block_device *bdev, sector_t secnum,
 	dev_info = bdev->bd_disk->private_data;
 	if (!dev_info)
 		return -ENODEV;
-	dev_sz = dev_info->end - dev_info->start;
+	dev_sz = dev_info->end - dev_info->start + 1;
 	offset = secnum * 512;
 	*kaddr = (void *) dev_info->start + offset;
 	*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset), PFN_DEV);