staging: erofs: switch to new decompression backend

This patch integrates new decompression framework to
erofs decompression path, and remove the old
decompression implementation as well.

On kirin980 platform, sequential read is slightly
improved to 778MiB/s after the new decompression
backend is used.

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