ocfs2: remove OCFS2_IOCB_SEM lock type in direct io

In ocfs2 direct read/write, OCFS2_IOCB_SEM lock type is used to protect
inode->i_alloc_sem rw semaphore lock in the earlier kernel version.
However, in the latest kernel, inode->i_alloc_sem rw semaphore lock is not
used at all, so OCFS2_IOCB_SEM lock type needs to be removed.

Signed-off-by: Weiwei Wang <wangww631@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Reviewed-by: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>