[clang] [llvm] [BPF] Add load-acquire and store-release instructions under -mcpu=v4 (PR #108636)

[Yingchi Long via cfe-commits]

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@@ -0,0 +1,142 @@
+; RUN: llc < %s -march=bpfel -mcpu=v4 -verify-machineinstrs -show-mc-encoding \
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inclyc wrote:

```suggestion
; RUN: llc < %s -march=bpfel -mcpu=v4 -verify-machineinstrs \
```

Maybe not test mc encoding again

https://github.com/llvm/llvm-project/pull/108636