[llvm] [AArch64][GlobalISel] Constrain G_CONSTANT_FOLD_BARRIER operand register classes (PR #177997)

[Ryan Cowan via llvm-commits]

HolyMolyCowMan wrote:

Is there a reason you fixed this in instruction select and not in regbankselect?

https://github.com/llvm/llvm-project/pull/177997