Remove cuda hard-code in compute_causal_conv1d_metadata (vllm-project#25555)

Signed-off-by: Icey <1790571317@qq.com>

Author: wxsIcey

vllm/v1/attention/backends/utils.py

@@ -947,6 +947,7 @@ def compute_causal_conv1d_metadata(query_start_loc_p: torch.Tensor):
     nums_dict = {}  # type: ignore
     batch_ptr = None
     token_chunk_offset_ptr = None
+    device = query_start_loc_p.device
     for BLOCK_M in [8]:  # cover all BLOCK_M values
         nums = -(-seqlens // BLOCK_M)
         nums_dict[BLOCK_M] = {}
@@ -968,11 +969,11 @@ def compute_causal_conv1d_metadata(query_start_loc_p: torch.Tensor):
             batch_ptr = torch.full((MAX_NUM_PROGRAMS, ),
                                    PAD_SLOT_ID,
                                    dtype=torch.int32,
-                                   device='cuda')
+                                   device=device)
             token_chunk_offset_ptr = torch.full((MAX_NUM_PROGRAMS, ),
                                                 PAD_SLOT_ID,
                                                 dtype=torch.int32,
-                                                device='cuda')
+                                                device=device)
         else:
             if batch_ptr.nelement() < MAX_NUM_PROGRAMS:
                 batch_ptr.resize_(MAX_NUM_PROGRAMS).fill_(PAD_SLOT_ID)