virtio-gpu: Fix memory leak in virtio_gpu_load()

Coverity points out that if we fail in the "creating resources"
loop in virtio_gpu_load() we will leak various resources (CID 1356431).
Failing a VM load is going to leave the simulation in a complete mess,
but we can tidy up to the point that a full system reset should
get us back to sanity.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1483969123-14839-3-git-send-email-peter.maydell@linaro.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
