Revert "drm: mark context support as a legacy subsystem"

This reverts commit 7c510133d93dd6f15ca040733ba7b2891ed61fd1.

Well looks like not enough digging was done, libdrm_nouveau before 2.4.33
used contexts,

292da616fe1f936ca78a3fa8e1b1b19883e343b6 nouveau: pull in major libdrm rewrite

got rid of them,

Reported-by: Paul Zimmerman <Paul.Zimmerman@synopsys.com>
Reported-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index 4be8e09..3f84277 100644
--- a/drivers/gpu/drm/drm_fops.c
+++ b/drivers/gpu/drm/drm_fops.c
@@ -439,7 +439,26 @@
 	if (dev->driver->driver_features & DRIVER_GEM)
 		drm_gem_release(dev, file_priv);
 
-	drm_legacy_ctxbitmap_release(dev, file_priv);
+	mutex_lock(&dev->ctxlist_mutex);
+	if (!list_empty(&dev->ctxlist)) {
+		struct drm_ctx_list *pos, *n;
+
+		list_for_each_entry_safe(pos, n, &dev->ctxlist, head) {
+			if (pos->tag == file_priv &&
+			    pos->handle != DRM_KERNEL_CONTEXT) {
+				if (dev->driver->context_dtor)
+					dev->driver->context_dtor(dev,
+								  pos->handle);
+
+				drm_ctxbitmap_free(dev, pos->handle);
+
+				list_del(&pos->head);
+				kfree(pos);
+				--dev->ctx_count;
+			}
+		}
+	}
+	mutex_unlock(&dev->ctxlist_mutex);
 
 	mutex_lock(&dev->struct_mutex);