[TPU][V1] Fix exponential padding when max-num-batched-tokens is not a power of 2

[NickLucche]

Currently if passing a non power of 2 max-num-batched-tokens will trigger the assert

vllm/vllm/v1/worker/tpu_model_runner.py

Line 1067 in 1dd2338

assert index < len(paddings)

This is because we're not padding for next bigger multiple of 2 power.
Eg.

# main
max-num-batched-tokens = 586
->padding [16, 32, 64, 128, 256, 512]

# with fix
max-num-batched-tokens = 586
->padding [16, 32, 64, 128, 256, 512, 1024]

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[mgoin]

Thanks!