drm: qxl: Embed drm_device into driver structure

This is the recommended way to create the drm_device structure,
according to DRM documentation.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170127010548.27970-4-krisman@collabora.co.uk


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>