Two problems - using wrong size type:
- process_compressed_read used blk_status_t for ret which is u8
so it can not process negative error codes and larger sizes
properly - fix this by changing it to int
- decompression fails for images with size larger than 2GB
due to wrong return type of parse_
Currently code uses only top qcow2 delta to handle decompression.
Images have compression type in the qcow2 header already set when loaded.
To support mixed compression switch to use qio->qcow2 and respective
qcow2 header so the decompression is performed with the correct type.
Remove qcow2 argume
