drm/nouveau/disp/nv50-: bump max chans to 21

commit a90e049c upstream.

GP102's cursors go from chan 17..20. Increase the array size to hold
their data properly.

Fixes: e50fcff1 ("drm/nouveau/disp/gp102: fix cursor/overlay immediate channel indices")
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/nouveau/nvkm/engine/disp/nv50.h

@@ -27,7 +27,7 @@ struct nv50_disp {
 		u8 type[3];
 	} pior;
 
-	struct nv50_disp_chan *chan[17];
+	struct nv50_disp_chan *chan[21];
 };
 
 int nv50_disp_root_scanoutpos(NV50_DISP_MTHD_V0);