[EPLB] Eplb Verify Fix (#4334)

### What this PR does / why we need it?
Eplb Verify Fix
---------

Signed-off-by: shenchuxiaofugui <[email protected]>
Signed-off-by: LI SHENGYONG <[email protected]>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: shenchuxiaofugui

vllm_ascend/ops/common_fused_moe.py

@@ -250,7 +250,8 @@ def __init__(self, *args, **kwargs):
                                         dtype=torch.int64).npu()
 
         eplb_enable = self.dynamic_eplb or (self.expert_map_path is not None)
-        if eplb_enable and (not isinstance(self.quant_method,
+        if eplb_enable and (not hasattr(self.quant_method, "quant_method") or
+                            not isinstance(self.quant_method.quant_method,
                                            AscendW8A8DynamicFusedMoEMethod)):
             raise ValueError("Eplb supports only w8a8_dynamic quantization.")