Function mamba2_ssd_bmm 

pub fn mamba2_ssd_bmm(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    b_proj: DevicePtr,
    c_proj: DevicePtr,
    cb: DevicePtr,
    seq_len: u32,
    nchunks: u32,
    n_groups: u32,
    state_size: u32,
    batch_size: u32,
    bc_stride: u32,
    stream: u64,
) -> Result<()>

K2: CB[c][g][t][s] = C_t . B_s (raw, fp32).