drm/nouveau/subdev: remove nvkm_subdev.mutex

There's not really any nice way to assign the lock classes when we split
subdev indices into type+inst, and saves a few bytes in the structs when
a subdev has no need for it.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>

drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h

@@ -7,7 +7,6 @@ struct nvkm_subdev {
 	const struct nvkm_subdev_func *func;
 	struct nvkm_device *device;
 	enum nvkm_devidx index;
-	struct mutex mutex;
 	u32 debug;
 
 	bool oneinit;

drivers/gpu/drm/nouveau/nvkm/core/subdev.c

@@ -26,8 +26,6 @@
 #include <core/option.h>
 #include <subdev/mc.h>
 
-static struct lock_class_key nvkm_subdev_lock_class[NVKM_SUBDEV_NR];
-
 const char *
 nvkm_subdev_name[NVKM_SUBDEV_NR] = {
 	[NVKM_SUBDEV_ACR     ] = "acr",
@@ -217,8 +215,6 @@ nvkm_subdev_ctor(const struct nvkm_subdev_func *func,
 	subdev->func = func;
 	subdev->device = device;
 	subdev->index = index;
-
-	__mutex_init(&subdev->mutex, name, &nvkm_subdev_lock_class[index]);
 	subdev->debug = nvkm_dbgopt(device->dbgopt, name);
 }