[Feat.][310P] addrmsnorm for 300I DUO (#6704)

### What this PR does / why we need it?
This PR integrates the `npu_add_rms_norm` fused kernel for RMSNorm
operations with residual connections on 310P devices. This change
optimizes the computation by replacing a two-step process (manual
residual addition followed by RMSNorm) with a single, more efficient
fused operation. This is needed to improve the performance of models
utilizing RMSNorm with residual connections on the 310P architecture.

Fixes #

### Does this PR introduce _any_ user-facing change?
No, this PR introduces an internal optimization and does not change any
user-facing APIs or behaviors.

### How was this patch tested?
This patch was tested with updated unit tests
(`test_RMSNorm_forward_310p`) that mock the `npu_add_rms_norm` operation
to verify the correctness of the fused kernel integration.

---------

Signed-off-by: Tflowers-0129 <2906339855@qq.com>

vllm_ascend/utils.py

@@ -628,13 +628,11 @@ def register_ascend_customop(vllm_config: VllmConfig | None = None):
         from vllm_ascend._310p.fused_moe.fused_moe import AscendFusedMoE310, AscendSharedFusedMoE310
         from vllm_ascend._310p.ops.activation import AscendSiluAndMul310
         from vllm_ascend._310p.ops.layernorm import AscendGemmaRMSNorm310, AscendRMSNorm310
-        from vllm_ascend._310p.ops.mm_encoder_attention import AscendMMEncoderAttention310
         from vllm_ascend._310p.ops.rotary_embedding import AscendRotaryEmbedding310
 
         REGISTERED_ASCEND_OPS.update(
             {
                 "SiluAndMul": AscendSiluAndMul310,
-                "MMEncoderAttention": AscendMMEncoderAttention310,
                 "RotaryEmbedding": AscendRotaryEmbedding310,
                 "RMSNorm": AscendRMSNorm310,
                 "GemmaRMSNorm": AscendGemmaRMSNorm310,