[ADT] Fix the initial size calculation of SmallDenseMap#158458

kazutakahirata merged 2 commits intollvm:mainllvm/llvm-project:mainfrom

kazutakahirata:cleanup_20250913_SmallDenseMap_initkazutakahirata/llvm-project:cleanup_20250913_SmallDenseMap_initCopy head branch name to clipboard