ide: Split qdev "ide-drive" into "ide-hd" and "ide-cd"

ide: Split qdev "ide-drive" into "ide-hd" and "ide-cd"

An "ide-drive" is either a hard disk or a CD-ROM, depending on the
associated BlockDriverState's type hint.  Unclean; disk vs. CD belongs
to the guest part, not the host part.

Have separate qdevs "ide-hd" and "ide-cd" to model disk vs. CD in
the guest part.

Keep ide-drive for backward compatibility.

"ide-disk" would perhaps be a nicer name than "ide-hd", but there's
already "scsi-disk", which is like "ide-drive", and will be likewise
split in the next commit.  {ide,scsi}-{hd,cd} is the best consistent
set of names I could find within the backward compatibility
straightjacket.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>