[Bugfix] Fix MRotaryEmbedding missing `truncate` attr with YaRN scaling (#35080)

Signed-off-by: haosdent <haosdent@gmail.com>

vllm/model_executor/layers/rotary_embedding/mrope.py

@@ -218,12 +218,14 @@ class MRotaryEmbedding(RotaryEmbeddingBase):
         attn_factor: float = 1,
         beta_fast: int = 32,
         beta_slow: int = 1,
+        truncate: bool = True,
     ) -> None:
         self.scaling_factor = scaling_factor
         self.extrapolation_factor = extrapolation_factor
         self.attn_factor = attn_factor
         self.beta_fast = beta_fast
         self.beta_slow = beta_slow
+        self.truncate = truncate
         if self.scaling_factor is not None:
             # Get n-d magnitude scaling corrected for interpolation
             self.mscale = float(yarn_get_mscale(self.scaling_factor) * attn_factor)