qxl: silence uninitialized variable warning

GCC doesn't complain about this but my static checker does.  We're
passing "drawable" before initializing it.  It's not actually used so
it's harmless and I just removed it.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160711084716.GB31411@mwanda

drivers/gpu/drm/qxl/qxl_draw.c

@@ -37,7 +37,6 @@ static int alloc_clips(struct qxl_device *qdev,
  * the qxl_clip_rects. This is *not* the same as the memory allocated
  * on the device, it is offset to qxl_clip_rects.chunk.data */
 static struct qxl_rect *drawable_set_clipping(struct qxl_device *qdev,
-					      struct qxl_drawable *drawable,
 					      unsigned num_clips,
 					      struct qxl_bo *clips_bo)
 {
@@ -351,7 +350,7 @@ void qxl_draw_dirty_fb(struct qxl_device *qdev,
 	if (ret)
 		goto out_release_backoff;
 
-	rects = drawable_set_clipping(qdev, drawable, num_clips, clips_bo);
+	rects = drawable_set_clipping(qdev, num_clips, clips_bo);
 	if (!rects)
 		goto out_release_backoff;