[GVN] Reuse dominating PtrToInt for PtrToAddr. (#209164)
A ptrtoaddr and a ptrtoint of the same pointer compute the same value
when the address width equals the pointer representation width. Reuse
a dominating ptrtoint in place of a ptrtoaddr.
This fixes a few end-to-end regressions with
https://github.com/llvm/llvm-project/pull/180244.
PR: https://github.com/llvm/llvm-project/pull/209164
