[llvm] [llvm][ARM][NFC] Renaming FeaturePrefLoopLogAlign (PR #109932)

[Nashe Mncube via llvm-commits]

nasherm wrote:

> Personally I would just kept it consistent with the subtarget feature spelling, e.g. FeatureLoopAlign to match loop-align. But I don't feel that strongly. If you're going to stick with the current suggestion then maybe expand "Pref" to "Prefer" since it only saves two characters.

I've renamed `loop-align` to `branch-align` to keep it consistent. Also changed "Pref" to "Prefer"

https://github.com/llvm/llvm-project/pull/109932