ui: rename cursor_{get->ref}, return it

The naming is more conventional in QEMU code, and allows to simplify
some code by changing the API design, so it returns the input parameter,
instead of void.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
5 files changed