nak: Emit !PT for carries on IADD3

They seem to be ignored by the hardware but the blob emits them.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29393>

src/nouveau/compiler/nak/encode_sm70.rs

@@ -1031,6 +1031,9 @@ impl SM70Instr {
             ALUSrc::from_src(&op.srcs[2]),
         );
 
+        self.set_pred_src(87..90, 90, false.into());
+        self.set_pred_src(77..80, 80, false.into());
+
         self.set_pred_dst(81..84, op.overflow[0]);
         self.set_pred_dst(84..87, op.overflow[1]);
     }