drm/qxl: drop unused offset parameter from qxl_io_create_primary()

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20190118122020.27596-12-kraxel@redhat.com