Check if flash attention is supported on the issue or not, and accordingly update on the benchmark specific readme

[Anindyadeep]

For each of the benchmark, check if Flash Attention v2 is present or not, if it is present, then use it and mention it on the benchmark specific readme too.

[nsosio]

@Anindyadeep can you update the issue with "check flash attention v2 support"?

[Anindyadeep]

@Anindyadeep can you update the issue with "check flash attention v2 support"?

Done