Recommit [AArch64] Optimize memcmp when the result is tested for [in]equality with 0

Fixes 1st issue of https://github.com/llvm/llvm-project/issues/58061
Fixes the crash of https://github.com/llvm/llvm-project/issues/58675

Reviewed By: dmgreen, efriedma
Differential Revision: https://reviews.llvm.org/D136244