[ROCm][AITER] bugfix accuracy regression in ROCM_AITER_TRITON_MLA backend (#31816)

Signed-off-by: vllmellm <vllm.ellm@embeddedllm.com>

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

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-from vllm.v1.attention.backends.mla.common import MLACommonBackend
-from vllm.v1.attention.backends.mla.rocm_aiter_mla import (
-    AiterMLAImpl,
-    AiterMLAMetadataBuilder,
-)
+from vllm.v1.attention.backends.mla.rocm_aiter_mla import AiterMLABackend, AiterMLAImpl
 
 
-class AiterTritonMLABackend(MLACommonBackend):
+class AiterTritonMLABackend(AiterMLABackend):
     @staticmethod
     def get_name() -> str:
         return "AITER_TRITON_MLA"
@@ -16,10 +12,6 @@ class AiterTritonMLABackend(MLACommonBackend):
     def get_impl_cls() -> type["AiterTritonMLAImpl"]:
         return AiterTritonMLAImpl
 
-    @staticmethod
-    def get_builder_cls() -> type["AiterMLAMetadataBuilder"]:
-        return AiterMLAMetadataBuilder
-
 
 class AiterTritonMLAImpl(AiterMLAImpl):
     def __init__(