drm/nouveau/fifo: turn all fifo modules into engine modules

Been tested on each major revision that's relevant here, but I'm sure there
are still bugs waiting to be ironed out.

This is a *very* invasive change.

There's a couple of pieces left that I don't like much (eg. other engines
using fifo_priv for the channel count), but that's an artefact of there
being a master channel list still.  This is changing, slowly.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nv84_fence.c

@@ -25,6 +25,7 @@
 #include "drmP.h"
 #include "nouveau_drv.h"
 #include "nouveau_dma.h"
+#include "nouveau_fifo.h"
 #include "nouveau_ramht.h"
 #include "nouveau_fence.h"
 
@@ -145,8 +146,8 @@ nv84_fence_destroy(struct drm_device *dev, int engine)
 int
 nv84_fence_create(struct drm_device *dev)
 {
+	struct nouveau_fifo_priv *pfifo = nv_engine(dev, NVOBJ_ENGINE_FIFO);
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
-	struct nouveau_fifo_engine *pfifo = &dev_priv->engine.fifo;
 	struct nv84_fence_priv *priv;
 	int ret;