[DeepSeek R1]Use UNIFORM QueryLen MLA for MTP

Author: ZhiweiYan-96

vllm/v1/attention/backends/mla/rocm_aiter_mla.py

@@ -81,7 +81,7 @@ class AiterMLAMetadataBuilder(MLACommonMetadataBuilder[AiterMLAMetadata]):
     # TODO(luka, lucas): audit this as part of:
     #  https://github.com/vllm-project/vllm/issues/22945
     cudagraph_support: ClassVar[AttentionCGSupport] = AttentionCGSupport.UNIFORM_BATCH
-    query_len_support: ClassVar[QueryLenSupport] = QueryLenSupport.VARLEN
+    query_len_support: ClassVar[QueryLenSupport] = QueryLenSupport.UNIFORM
 
     def __init__(
         self,