fix typo in assignment of fs default overflow gid

The patch remains without practical effect since both macros carry
identical values.  Still, it might become a problem in the future if
(for whatever reason) the default overflow uid and gid differ.  The
DEFAULT_FS_OVERFLOWGID macro was previously unused.
Signed-off-by: Wolffhardt Schwabe <wolffhardt.schwabe@fau.de>
Signed-off-by: Anatoliy Cherepantsev <anatoliy.cherepantsev@fau.de>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

kernel/sys.c

@@ -135,7 +135,7 @@ EXPORT_SYMBOL(overflowgid);
  */
 
 int fs_overflowuid = DEFAULT_FS_OVERFLOWUID;
-int fs_overflowgid = DEFAULT_FS_OVERFLOWUID;
+int fs_overflowgid = DEFAULT_FS_OVERFLOWGID;
 
 EXPORT_SYMBOL(fs_overflowuid);
 EXPORT_SYMBOL(fs_overflowgid);