[llvm] [AArch64] Enable dead register definitions at O0 (PR #145174)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

> The point is that it should resolve to aliases for better understanding, which is why -O0 exists to begin with.

This is not true 

https://github.com/llvm/llvm-project/pull/145174