fix ub overflow in move_cache_dynamic_last_kernel_h_block kernel

[Li-brua]

Fix Triton compilation failure caused by UB overflow in
move_cache_dynamic_last_kernel_h_block on Ascend NPUs. See issue: sgl-project/sglang#25330

The previous implementation only tiled the H dimension while fully materializing
V x K blocks:

BLOCK_V = triton.next_power_of_2(V)
BLOCK_K = triton.next_power_of_2(K)

For large V/K values, this could generate oversized temporary buffers during
BiShengHIR lowering and fail with:

ub overflow, requires 2097152 bits while 1572864 bits available

This PR additionally tiles V and K dimensions to reduce per-tile UB usage and added upper bounds for Triton block sizes to avoide overflow.

[gemini-code-assist]

Warning

You have reached your daily quota limit. Please wait up to 24 hours and I will start processing your requests again!