[WIP][Attention] Update FlashMLA

[LucasWilkinson]

Update to the latest FlashMLA

Accuracy

VLLM_USE_V1=0 lm_eval --model vllm --model_args pretrained=deepseek-ai/DeepSeek-V2-Lite-Chat,tensor_parallel_size=2,dtype=auto,gpu_memory_utilization=0.9,trust_remote_code=True,max_model_len=16384 --task gsm8k --num_fewshot 5  --batch_size auto

|Tasks|Version|     Filter     |n-shot|  Metric   |   |Value |   |Stderr|
|-----|------:|----------------|-----:|-----------|---|-----:|---|-----:|
|gsm8k|      3|flexible-extract|     5|exact_match|↑  |0.6634|±  |0.0130|
|     |       |strict-match    |     5|exact_match|↑  |0.6596|±  |0.0131|

VLLM_USE_V1=1 lm_eval --model vllm --model_args pretrained=deepseek-ai/DeepSeek-V2-Lite-Chat,tensor_parallel_size=2,dtype=auto,gpu_memory_utilization=0.9,trust_remote_code=True,max_model_len=16384 --task gsm8k --num_fewshot 5  --batch_size auto

|Tasks|Version|     Filter     |n-shot|  Metric   |   |Value |   |Stderr|
|-----|------:|----------------|-----:|-----------|---|-----:|---|-----:|
|gsm8k|      3|flexible-extract|     5|exact_match|↑  |0.6710|±  |0.0129|
|     |       |strict-match    |     5|exact_match|↑  |0.6626|±  |0.0130|

Benchmarking 8xH200 DeepSeek-R1

main

  input_tokens output_tokens  vllm_output_toks/s
0         1000          2000         1147.119850
1         5000          1000          883.519124
2        10000           500          472.130590
3        30000           100           43.572829
4     sharegpt      sharegpt         1387.960241

this PR

  input_tokens output_tokens  vllm_output_toks/s
0         1000          2000         1118.442740
1         5000          1000          867.962366
2        10000           500          466.229469
3        30000           100           43.298352
4     sharegpt      sharegpt         1376.845286

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[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @LucasWilkinson.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[hmellor]

Closing as stale