UBI: set correct gluebi device size

In case of static volumes, make emulated MTD device size to
be equivalent to data size, rather then volume size.

Reported-by: John Smith <john@arrows.demon.co.uk>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/cdev.c

@@ -397,6 +397,7 @@ static ssize_t vol_cdev_write(struct file *file, const char __user *buf,
 			vol->corrupted = 1;
 		}
 		vol->checked = 1;
+		ubi_gluebi_updated(vol);
 		revoke_exclusive(desc, UBI_READWRITE);
 	}