ocfs2: Fix system inodes cache overflow.

When we store system inodes cache in ocfs2_super,
we use a array for global system inodes. But unfortunately,
the range is calculated wrongly which makes it overflow and
pollute ocfs2_super->local_system_inodes.
This patch fix it by setting the range properly.

The corresponding bug is ossbug1303.
http://oss.oracle.com/bugzilla/show_bug.cgi?id=1303

Cc: stable@kernel.org
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>