[llvm] [InlineAsm] refactor InlineAsm class NFC (PR #65649)

[James Y Knight via llvm-commits]

https://github.com/jyknight approved this pull request.

Just a sidenote: multiple overlapping Bitfield::Element could be used for "Data", if desired. I don't think it matters here, so approving as is. But, it would be useful if we wanted to add additional fields for only some of the options later (e.g. Mem Constraint code doesn't need as many bits as it's given, so other data could fit next to it in that case).

https://github.com/llvm/llvm-project/pull/65649