[clang] [llvm] [AArch64] Rename memory hints to avoid clash with arm_acle.h macros (PR #226432)

[Kerry McLaughlin via llvm-commits]

kmclaughlin-arm wrote:

> Do you think it's worth changing arm_acle.h to use `const int` rather than a macro?

I've changed the hints in arm_acle.h to `const int`, but also removed `MEM_HINT` from the hint names in LLVM since these will be prefixed by `AArch64MemoryHint`.

https://github.com/llvm/llvm-project/pull/226432