drm/vboxvideo: Switch to generic fbdev emulation

There's nothing special about vboxvideo's fbdev emulation that is
not provided by the generic implementation. Switch over and remove
the driver's code.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191011134808.3955-2-tzimmermann@suse.de

drm/vbox: Remove empty PRIME functions

The vbox driver uses VRAM helpers for memory management. These helpers
provide a basic implementation of PRIME functions, so the vbox driver's
empty implmentation can be removed. As a side effect of this change,
vbox can now use generic framebuffer emulation.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190702115012.4418-5-tzimmermann@suse.de

drm/vboxvideo: Move the vboxvideo driver out of staging

The vboxvideo driver has been converted to the atomic modesetting API
and all FIXME and TODO items have been fixed, so it is time to move it out
of staging.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190304164724.10210-4-hdegoede@redhat.com