fs/yaffs2: adjust to the change of inode_change_ok()

In commit cb8e1eef ("fs: Give dentry to inode_change_ok() instead
of inode") the inode_change_ok() has been rename to setattr_prepare(),
and one of the argument was also changed from inode to dentry. We
adjust the invocation of inode_change_ok() in Yaffs2 according to
this change.

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>