[llvm] [LLVM][DAGCombiner] Fix size calculations in calculateByteProvider. (PR #148425)

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

@arsenm - The PR has change direction, tis now much simpler, after you accepted it.  Do you mind taking another look to make sure you're still happy with it?

https://github.com/llvm/llvm-project/pull/148425