[llvm] [AMDGPU][GlobalISel] Pre-commit tests for readanylane merge regbank combine (NFC) (PR #214355)

[Matt Arsenault via llvm-commits]

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+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 6
+# RUN: llc -mtriple=amdgpu12.00-amd-amdhsa -mcpu=gfx1200 -run-pass=amdgpu-regbank-combiner %s -verify-machineinstrs -o - | FileCheck %s
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arsenm wrote:

```suggestion
# RUN: llc -mtriple=amdgpu12.00-amd-amdhsa -run-pass=amdgpu-regbank-combiner %s -verify-machineinstrs -o - | FileCheck %s
```

https://github.com/llvm/llvm-project/pull/214355