ocfs2: fix super block reserved field offset comment

The offset annotation for s_reserved2 in struct ocfs2_super_block
was incorrect. After the preceding fields:
- s_xattr_inline_size (2 bytes at 0xB8)
- s_reserved0 (2 bytes at 0xBA)
- s_dx_seed[3] (12 bytes at 0xBC)

The actual offset of s_reserved2 is at 0xC8, when calculating from the
start of the structure.

Correct the offset comment from C0 to C8 to reflect the proper location in
the super block structure.

Link: https://lkml.kernel.org/r/20250807155749.164481-1-yili@winhong.com
Signed-off-by: yili <yili@winhong.com>
Reviewed-by: Joel Becker <jlbec@evilplan.org>
Acked-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>