Fix get_nvl_buffer_size_hint and get_rdma_buffer_size_hint

[yuantailing]

If I understand correctly,

1. L62 is corresponding to

   DeepEP/csrc/kernels/internode.cu

   Line 416 in e02e4d2

   auto rdma_channel_meta = SymBuffer<int>(rdma_buffer_ptr, NUM_MAX_NVL_PEERS * 2 + 2, kNumRDMARanks, channel_id, num_channels);

2. L67 is corresponding to

   DeepEP/csrc/kernels/internode.cu

   Lines 579 to 581 in e02e4d2

   	auto idx_value = static_cast<int>(ld_nc_global(topk_idx + token_idx * num_topk + copy_idx));
   	auto weight_value = ld_nc_global(topk_weights + token_idx * num_topk + copy_idx);
   	st_na_global(reinterpret_cast<int*>(dst_send_buffers[rank_idx]) + copy_idx, idx_value);

   , and it is also counted as sizeof(int) in get_num_bytes_per_token
3. L70 is corresponding to int4 alignment:

   DeepEP/csrc/kernels/internode.cu

   Lines 45 to 47 in e02e4d2

   	int get_num_bytes_per_token(int hidden_int4, int num_scales, int num_topk_idx, int num_topk_weights) {
   	return static_cast<int>(align_up(hidden_int4 * sizeof(int4) + sizeof(SourceMeta) + num_scales * sizeof(float) + num_topk_idx * sizeof(int) + num_topk_weights * sizeof(float), sizeof(int4)));
   	}

4. L94 is similar to L67
5. L98 is corresponding to

   DeepEP/csrc/kernels/internode.cu

   Lines 417 to 418 in e02e4d2

   	auto rdma_channel_head = SymBuffer<uint64_t, false>(rdma_buffer_ptr, 1, kNumRDMARanks, channel_id, num_channels);
   	auto rdma_channel_tail = SymBuffer<uint64_t, false>(rdma_buffer_ptr, 1, kNumRDMARanks, channel_id, num_channels);

Before change:

>>> deep_ep.Config(24, 8, 512, 16, 128).get_nvl_buffer_size_hint(7168, 16)
453380736
>>> deep_ep.Config(24, 8, 512, 16, 128).get_rdma_buffer_size_hint(7168, 16)
56774016

After change:

>>> deep_ep.Config(24, 8, 512, 16, 128).get_nvl_buffer_size_hint(7168, 16)
429000960
>>> deep_ep.Config(24, 8, 512, 16, 128).get_rdma_buffer_size_hint(7168, 16)
53629056