[llvm] [TableGen] Don't instantiate CodeGenDAGPatterns where unnecessary (PR #115689)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

The reason is described near `guessInstructionProperties` in `Target.td`.
If this field is set to true, some instruction properties (namely, `mayLoad`, `mayStore` and `hasSideEffects`) are inferred from the first pattern for the instruction. This does not happen if `CodeGenDAGPatterns` is not instantiated.


https://github.com/llvm/llvm-project/pull/115689