erofs: correct the remaining shrink objects

erofs: correct the remaining shrink objects

commit 5334ebe3d0fbbc538c265d0ac1c969da8abebbe0 upstream.

The remaining count should not include successful
shrink attempts.

Fixes: 18c442aa52dc ("staging: erofs: introduce workstation for decompression")
Cc: <stable@vger.kernel.org> # 4.19+
Link: https://lore.kernel.org/r/20200226081008.86348-1-gaoxiang25@huawei.com
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>