qdev: Tag isa-fdc, PIIX3 IDE and PIIX4 IDE as no-user

These devices are created automatically, and attempting to create
another one with -device fails with "qemu: hardware error:
register_ioport_write: invalid opaque".

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
