[llvm] [ARM] Change the type of CC and VCC code in `splitMnemonic`. (PR #83413)

[Alfie Richards via llvm-commits]

AlfieRichardsArm wrote:

@s-barannikov I've added you as a reviewer as this commit is a prerequisite for some optional operands work that I will submit in coming days and I see you have worked on the same area.

https://github.com/llvm/llvm-project/pull/83413