qapi/qom: Add ObjectOptions for rng-*, deprecate 'opened'

qapi/qom: Add ObjectOptions for rng-*, deprecate 'opened'

This adds a QAPI schema for the properties of the rng-* objects.

The 'opened' property doesn't seem to make sense as an external
interface: It is automatically set to true in ucc->complete, and
explicitly setting it to true earlier just means that trying to set
additional options will result in an error. After the property has once
been set to true (i.e. when the object construction has completed), it
can never be reset to false. In other words, the 'opened' property is
useless. Mark it as deprecated in the schema from the start.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>