[v0.18.0][Bugfix] fix ds3.2 dcp mtp (#7681)

### What this PR does / why we need it?
Fixed the issue where the DCP overlaps the MTP scenario in the ds3.2
scenario.

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?

cherry-pick from: https://github.com/vllm-project/vllm-ascend/pull/7617

Signed-off-by: weiguihua2 <weiguihua2@huawei.com>

vllm_ascend/spec_decode/eagle_proposer.py

@@ -600,7 +600,7 @@ class SpecDecodeBaseProposer(EagleProposer):
                     - 1
                 )
                 num_accept_tokens = query_lens_d.to(self.device) - num_reject_tokens
-                ori_seq_len = attn_metadata_i.seq_lens[:batch_size].clone()
+                ori_seq_len = attn_metadata_i.seq_lens_cpu[:batch_size].clone()
                 mtp_slot_mapping = self.runner.pcp_manager.mtp_slot_pad
 
                 # slot_mapping index base offset:
@@ -1247,7 +1247,8 @@ class SpecDecodeBaseProposer(EagleProposer):
 
         if self.pcp_size * self.dcp_size > 1:
             if self.vllm_config.model_config.use_mla:
-                attn_metadata.decode.cp_seq_len = cp_seq_len
+                if getattr(attn_metadata, "decode", None):
+                    attn_metadata.decode.cp_seq_len = cp_seq_len
             else:
                 attn_metadata.decode_meta.num_computed_tokens_of_pcp_dcp = num_computed_tokens_of_pcp_dcp