UBIFS: fix the dark space calculation

The dark space calculation should be 64 bit type-casted, when
assigning to tmp64 (similar to how total_free is calculated).
Overflow will occur for very large flashes.

Signed-off-by: srimugunthan <srimugunthan.dhandapani@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@intel.com>
diff --git a/fs/ubifs/recovery.c b/fs/ubifs/recovery.c
index af02790..ee4f43f 100644
--- a/fs/ubifs/recovery.c
+++ b/fs/ubifs/recovery.c
@@ -983,7 +983,7 @@
 }
 
 /**
- *  clean_an_unclean_leb - read and write a LEB to remove corruption.
+ * clean_an_unclean_leb - read and write a LEB to remove corruption.
  * @c: UBIFS file-system description object
  * @ucleb: unclean LEB information
  * @sbuf: LEB-sized buffer to use