[clang] [llvm] AMDGPU: Add gfx12-generic target (PR #93875)

[Shilei Tian via cfe-commits]

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@@ -799,11 +799,12 @@ enum : unsigned {
   EF_AMDGPU_MACH_AMDGCN_RESERVED_0X56 = 0x056,
   EF_AMDGPU_MACH_AMDGCN_RESERVED_0X57 = 0x057,
   EF_AMDGPU_MACH_AMDGCN_RESERVED_0X58 = 0x058,
+  EF_AMDGPU_MACH_AMDGCN_GFX12_GENERIC     = 0x059,
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shiltian wrote:

```suggestion
  EF_AMDGPU_MACH_AMDGCN_GFX12_GENERIC  = 0x059,
```

https://github.com/llvm/llvm-project/pull/93875