support input_pos > 0 for prefill model

[billmguo]

Summary: test input_pos>0 for prefill, not intention for landing but for sync with qc

Differential Revision: D68847677

[pytorch-bot]

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❌ 2 New Failures, 2 Unrelated Failures

As of commit 38d22fb with merge base 92e7dbd ():

NEW FAILURES - The following jobs have failed:

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• Lint / lintrunner / linux-job (gh)
  >>> Lint for examples/qualcomm/oss_scripts/llama/model/static_llama.py:

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👉 Rebase onto the `viable/strict` branch to avoid these failures

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This pull request was exported from Phabricator. Differential Revision: D68847677

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[billmguo]

let me explain a little on this, Tokens, freq_cos, freq_sin, mask, k, v caches will be passed in both prefill and decode model
The freq_cos /freq_sin/mask . Here we remove input_pos since prefill model inference will be like AR-pre_fill_len model , the input_pos does not come into play, runtime can fill freq_cos/freq_sin/kv/mask information directly. let me know about your thoughts, in case you have better ideas to support multi-turn, that will be great!