Revert "GlobalISel/AArch64: don't optimize away redundant branches at -O0"

This reverts commit 458c230b.

This broke LLDB buildbot testcase where breakpoint set at start of loop
failed to hit. https://lab.llvm.org/buildbot/#/builders/96/builds/9404

https://github.com/llvm/llvm-project/blob/main/lldb/test/API/commands/process/attach/main.cpp#L15

Differential Revision: https://reviews.llvm.org/D105238