drm: kill context_ctor callback

It's not used by any driver. The destructor callback is unfortunately
used by the via driver in a rather convoluted piece of code used
to reimplement something resembling broken futexes. I didn't dare
to touch this code. But at least kill the needless NULL assignemt
in the sis driver.
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_context.c

@@ -333,14 +333,6 @@ int drm_addctx(struct drm_device *dev, void *data,
 		return -ENOMEM;
 	}
 
-	if (ctx->handle != DRM_KERNEL_CONTEXT) {
-		if (dev->driver->context_ctor)
-			if (!dev->driver->context_ctor(dev, ctx->handle)) {
-				DRM_DEBUG("Running out of ctxs or memory.\n");
-				return -ENOMEM;
-			}
-	}
-
 	ctx_entry = kmalloc(sizeof(*ctx_entry), GFP_KERNEL);
 	if (!ctx_entry) {
 		DRM_DEBUG("out of memory\n");

drivers/gpu/drm/sis/sis_drv.c

@@ -67,7 +67,6 @@ static struct drm_driver driver = {
 	.driver_features = DRIVER_USE_AGP | DRIVER_USE_MTRR,
 	.load = sis_driver_load,
 	.unload = sis_driver_unload,
-	.context_dtor = NULL,
 	.dma_quiescent = sis_idle,
 	.reclaim_buffers = NULL,
 	.reclaim_buffers_idlelocked = sis_reclaim_buffers_locked,

include/drm/drmP.h

@@ -700,7 +700,6 @@ struct drm_driver {
 	int (*resume) (struct drm_device *);
 	int (*dma_ioctl) (struct drm_device *dev, void *data, struct drm_file *file_priv);
 	int (*dma_quiescent) (struct drm_device *);
-	int (*context_ctor) (struct drm_device *dev, int context);
 	int (*context_dtor) (struct drm_device *dev, int context);
 
 	/**