[PATCH] drm/virtio: new ioctl for pinning and lazy pinning

First patch implements new ioctl. If there are no pages pinned to bo object, then pin it.

Second patch implements concepts of lazy pin. Userspace must opt-in for not pinning pages.

I would like to record this work here and investigate another possibility.

Mainly, problem statement for this two patches is to reduce memory usage consumed by Guest. If we can avoid pinning pages for such resources like textures, then we can use staging buffer to upload texture data to host.