Remove occurrences of unused struct qxl_device pointer in functions
qxl_ttm_fault() and qxl_init_mem_type().

Detected by Coverity: CID 1019128, CID 1019129.
Signed-off-by: NChristian Engelmayer <cengelma@gmx.at>
Signed-off-by: NDave Airlie <airlied@redhat.com>