ocfs2: Remove the redundant cpu_to_le64.

In ocfs2_block_group_alloc, we set c_blkno by bg->bg_blkno.
But actually bg->bg_blkno is already changed to little endian
in ocfs2_block_group_fill. So remove the extra cpu_to_le64.

Reported-by: Marcos Matsunaga <Marcos.Matsunaga@oracle.com>
Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>