update kv_cache_dtype support

vllm/attention/layer.py

@@ -130,8 +130,8 @@ def _init_kv_cache_quant(
         assert isinstance(quant_method, BaseKVCacheMethod)
         # TODO (mgoin): kv cache dtype should be specified in the FP8
         # checkpoint config and become the "auto" behavior
-        if layer.kv_cache_dtype == "fp8_e5m2":
-            raise ValueError("fp8_e5m2 kv-cache is not supported with fp8 checkpoints.")
+        # if layer.kv_cache_dtype == "fp8_e5m2":
+        #     raise ValueError("fp8_e5m2 kv-cache is not supported with fp8 checkpoints.")
         # If quantization is enabled, we make "k_scale" and "v_scale"
         # parameters so that it can be loaded from the model checkpoint.
         # The k/v_scale will then be converted back to native float32