staging: vboxvideo: Atomic phase 3: Switch last bits over to atomic

Now that the state objects are wired up, we can:

1) Move to the final atomic handlers
2) Wire up atomic set_config helper
3) Switch to drm_mode_config_helper_suspend/resume for suspend/resume
4) Enable atomic modesetting ioctl

This is all done in one commit because doing this piecemeal leads to
an intermediate state which triggers WARN_ONs in the atomic code because
e.g. plane->fb is still being set.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>