[llvm] [AArch64][SVE] Fold ADD+CNTB to INCB and DECB (PR #118280)

[Sjoerd Meijer via llvm-commits]

sjoerdmeijer wrote:

> Look ugly and should be avoided (even though the particular test causing this is a bit artificial and doesn't seem to be concerned with the particular pattern of ADDVL or MOV+INCB used).

I was trying to say that it doesn't look ugly to me because it is faster and uses the same (number of) registers.  

https://github.com/llvm/llvm-project/pull/118280