* allow to handle a maximum of packets in parallel
that fits free slots in the ack queue
* stop processing packets, when the driver can't handle
more requests in parallel, and resume packet handling,
when the driver is ready again
Use NATIVE MAX ADDRESS EXT to retrieve last block for LBA48. Also check not only
for enabled LBA48 support but for the 'host protected area' bit before using the
LBA48 version. This is because the high order byte (HOB) data retrieval is
broken in Qemu.
Fixes#761.
