staging: erofs: integrate decompression inplace

Decompressor needs to know whether it's a partial
or full decompression since only full decompression
can be decompressed in-place.

On kirin980 platform, sequential read is finally
increased to 812MiB/s after decompression inplace
is enabled.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>