[bugfix] fix megatron-swift seq_cls (#6115)

Author: Jintao-Huang

swift/megatron/model/gpt_model.py

@@ -250,9 +250,9 @@ def forward(
             logits, _ = self.output_layer(
                 hidden_states, weight=output_weight, runtime_gather_output=runtime_gather_output)
         else:
-            logits = self.output_layer(hidden_states)[0]
             if args.sequence_parallel and args.tensor_model_parallel_size > 1:
-                logits = gather_from_sequence_parallel_region(logits)
+                hidden_states = gather_from_sequence_parallel_region(hidden_states)
+            logits = self.output_layer(hidden_states)[0]
         if has_config_logger_enabled(self.config):
             payload = OrderedDict({
                 'input_ids': input_ids,