Revert "drm/nouveau: inform userspace of new kernel subchannel requirements"

This reverts commit a81f15499887d3f9f24ec70bb9b7e778942a6b7b.

Gah, we have a released userspace component using fixed subc assignment
that conflicts with this.  To avoid breaking ABI this needs to be
reverted.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/nouveau_dma.h b/drivers/gpu/drm/nouveau/nouveau_dma.h
index bcf0fd9..23d4edf 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dma.h
+++ b/drivers/gpu/drm/nouveau/nouveau_dma.h
@@ -48,8 +48,8 @@
 
 /* Hardcoded object assignments to subchannels (subchannel id). */
 enum {
-	NvSubSw		= 0,
-	NvSubM2MF	= 1,
+	NvSubM2MF	= 0,
+	NvSubSw		= 1,
 	NvSub2D		= 2,
 	NvSubCtxSurf2D  = 2,
 	NvSubGdiRect    = 3,