[llvm] [AMDGPU] Remove implicit conversions of MCRegister to unsigned. NFC (PR #167284)

[Sergei Barannikov via llvm-commits]

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@@ -1214,7 +1214,7 @@ static unsigned CheckVGPROverflow(unsigned Reg, const MCRegisterClass &RC,
 
   assert(BaseReg && "Only vector registers expected");
 
-  return (Sub0 - BaseReg + NumRegs <= 256) ? Reg : AMDGPU::NoRegister;
+  return (Sub0 - BaseReg + NumRegs <= 256) ? Reg : MCRegister();
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s-barannikov wrote:

If you're inclined to leaving the operator out, `[[deprecated]]` on it could help detect such cases without breaking the build


https://github.com/llvm/llvm-project/pull/167284