[llvm] [PowerPC] Utilize `getReservedRegs` to find asm clobberable registers. (PR #99766)

[Kai Luo via llvm-commits]

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@@ -1,7 +1,7 @@
 ; RUN: llc < %s -verify-machineinstrs -mtriple=powerpc-unknown-unkown \
-; RUN:   -mcpu=pwr7 2>&1 | FileCheck %s
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bzEq wrote:

Why change to `O0`?

https://github.com/llvm/llvm-project/pull/99766