optimized dsv3.2 missing underscore

[gronsti-amd]

ROCMAiterMLASparseMetadataBuilder sets cudagraph_support, but the actual checked name is _cudagraph_support.
This causes the default value AttentionCGSupport.NEVER to be used instead of the intended AttentionCGSupport.UNIFORM_SINGLE_TOKEN_DECODE

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[tvirolai-amd]

It's critical that DS3.2 has full graphs on decode. Some perf numbers: Single decode step went down from 59ms to 29ms. This is pretty much 100% speedup in this particular case on this particular node (MI300X) with a slow CPU .

There are some additional warnings in the logs so the real PR may need to retest and change things now that the graphs actually work, but they simply must work before it goes in as it's so critical for performance.