[llvm] [GISel][RISCV] Legalize G_CONSTANT_FOLD_BARRIER (PR #89960)

[Michael Maitland via llvm-commits]

https://github.com/michaelmaitland commented:

Do you plan on doing regbankselect and instructionselect in a different patch?

https://github.com/llvm/llvm-project/pull/89960