drm/nouveau/core: remove nouveau_mm.mutex, no more users

Signed-off-by: Ben Skeggs <[e-mail]>

drivers/gpu/drm/nouveau/core/core/mm.c

···
 	struct nouveau_mm_node *node;
 
 	if (block) {
-		mutex_init(&mm->mutex);
 		INIT_LIST_HEAD(&mm->nodes);
 		INIT_LIST_HEAD(&mm->free);
 		mm->block_size = block;

drivers/gpu/drm/nouveau/core/include/core/mm.h

···
 	struct list_head nodes;
 	struct list_head free;
 
-	struct mutex mutex;
-
 	u32 block_size;
 	int heap_nodes;
 };

drivers/gpu/drm/nouveau/nouveau_ttm.c

···
 	struct nouveau_mm_node *r;
 	u32 total = 0, free = 0;
 
-	mutex_lock(&mm->mutex);
+	mutex_lock(&nv_subdev(pfb)->mutex);
 	list_for_each_entry(r, &mm->nodes, nl_entry) {
 		printk(KERN_DEBUG "%s %d: 0x%010llx 0x%010llx\n",
 		       prefix, r->type, ((u64)r->offset << 12),
···
 		if (!r->type)
 			free += r->length;
 	}
-	mutex_unlock(&mm->mutex);
+	mutex_unlock(&nv_subdev(pfb)->mutex);
 
 	printk(KERN_DEBUG "%s  total: 0x%010llx free: 0x%010llx\n",
 	       prefix, (u64)total << 12, (u64)free << 12);