UPSTREAM: erofs: initialize packed inode after root inode is assigned

As commit 8f7acdae ("staging: erofs: kill all failure handling in
fill_super()"), move the initialization of packed inode after root
inode is assigned, so that the iput() in .put_super() is adequate as
the failure handling.

Otherwise, iput() is also needed in .kill_sb(), in case of the mounting
fails halfway.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Fixes: b15b2e30 ("erofs: support on-disk compressed fragments data")
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Acked-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230407141710.113882-3-jefflexu@linux.alibaba.com


Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
(cherry picked from commit cb9bce79
    https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git

 dev)
Bug: 296824280

Change-Id: I3cec91605b42c588e2c8f69629f0bdcc20078de2
Signed-off-by: sunshijie <sunshijie@xiaomi.corp-partner.google.com>
Signed-off-by: sunshijie <sunshijie@xiaomi.com>