drm/nouveau/ltc: fix tag base address getting truncated if above 4GiB

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

drivers/gpu/drm/nouveau/core/subdev/ltc/gf100.c

@@ -156,7 +156,7 @@ gf100_ltc_init_tag_ram(struct nouveau_fb *pfb, struct nvkm_ltc_priv *priv)
 	if (ret) {
 		priv->num_tags = 0;
 	} else {
-		u64 tag_base = (priv->tag_ram->offset << 12) + tag_margin;
+		u64 tag_base = ((u64)priv->tag_ram->offset << 12) + tag_margin;
 
 		tag_base += tag_align - 1;
 		ret = do_div(tag_base, tag_align);