Commit bcada37 dropped the (up to now undocumented) members type, len,
offset, speed, breaking tests/qemu-iotests/040 and 041.
Restore and document them. This fixes 040, and partially fixes 041.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Tested-By: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>