Their last user went away in commit f51074cd, "pci-hotplug-old: Has
been dead for five major releases, bury", v2.3.0.  Remove them, as new
code should use QemuOpts or maybe keyval_parse() instead.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20171006131645.17729-1-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>