Cutlass MLA decode - fix dtype error (sgl-project#5868)

Author: trevor-m

python/sglang/srt/layers/attention/cutlass_mla_backend.py

@@ -268,7 +268,7 @@ def forward_decode(
         reshape_q = q.view(-1, layer.tp_q_head_num, layer.head_dim)
 
         o = cutlass_mla_decode(
-            q_nope_and_q_pe=reshape_q,
+            q_nope_and_q_pe=reshape_q.to(self.q_data_type),
             kv_c_and_k_pe_cache=k_cache.view(-1, PAGE_SIZE, self.kv_cache_dim),
             seq_lens=forward_batch.seq_lens.to(torch.int32),
             page_table=self.forward_metadata.block_kv_indices,