[llvm] [NFCI][MC][DecoderEmitter] Fix BitWidth for fixed length inst encodings (PR #154934)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

> Or ignore size at all and only use it when generating table names. That is, treat size the same way as namespace.

Note that ignoring this MaxFilterWidth introduced in #154916 only affects a few lines in the generated file -- without it, some ExtractFields extract more bits than necessary. This should be harmless, I think.


https://github.com/llvm/llvm-project/pull/154934