drm/nouveau: Add a separate class for the kernel channel mutex.

nouveau_bo_move_m2mf() needs to lock the kernel channel, and it may be
called from the pushbuf IOCTL with an user channel already locked. Use
a separate subclass for the kernel channel mutex because this is
legitimate mutex nesting.

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.h b/drivers/gpu/drm/nouveau/nouveau_drv.h
index 5814db8..ce0475e 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drv.h
+++ b/drivers/gpu/drm/nouveau/nouveau_drv.h
@@ -173,6 +173,11 @@
 	uint64_t offset;
 };
 
+enum nouveau_channel_mutex_class {
+	NOUVEAU_UCHANNEL_MUTEX,
+	NOUVEAU_KCHANNEL_MUTEX
+};
+
 struct nouveau_channel {
 	struct drm_device *dev;
 	int id;