drm/nv50-/disp: add method descriptions for debugging

Lists of known methods for the DMA channel classes, and mappings to
their priv register addresses (where known).

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/core/engine/disp/nva3.c b/drivers/gpu/drm/nouveau/core/engine/disp/nva3.c
index aaf16c1..46cb2ce 100644
--- a/drivers/gpu/drm/nouveau/core/engine/disp/nva3.c
+++ b/drivers/gpu/drm/nouveau/core/engine/disp/nva3.c
@@ -111,4 +111,8 @@
 		.init = _nouveau_disp_init,
 		.fini = _nouveau_disp_fini,
 	},
+	.mthd.core = &nv94_disp_mast_mthd_chan,
+	.mthd.base = &nv84_disp_sync_mthd_chan,
+	.mthd.ovly = &nv84_disp_ovly_mthd_chan,
+	.mthd.prev = 0x000004,
 }.base.base;