[Model] Remove the unnecessary dtype conversion in MiniCPM (#32523)

Signed-off-by: gcanlin <canlinguosdu@gmail.com>

vllm/model_executor/models/minicpm.py

@@ -300,10 +300,7 @@ class MiniCPMAttention(nn.Module):
     ) -> torch.Tensor:
         qkv, _ = self.qkv_proj(hidden_states)
         q, k, v = qkv.split([self.q_size, self.kv_size, self.kv_size], dim=-1)
-        orig_dtype = q.dtype
-        q, k = q.float(), k.float()
         q, k = self.rotary_emb(positions, q, k)
-        q, k = q.to(orig_dtype), k.to(orig_dtype)
         attn_output = self.attn(q, k, v)
         output, _ = self.o_proj(attn_output)
         return output