[llvm] [AMDGPU] Fix undivergent parameter pass using vgpr (PR #178198)

[Shilei Tian via llvm-commits]

================
@@ -30,6 +30,7 @@ namespace ISD {
     unsigned IsSExt : 1;     ///< Sign extended
     unsigned IsNoExt : 1;    ///< No extension
     unsigned IsInReg : 1;    ///< Passed in register
+    unsigned IsArgInReg : 1; ///< Is caller function's 'inreg' argument
----------------
shiltian wrote:

I'm confused by `IsInReg` vs `IsArgInReg`

https://github.com/llvm/llvm-project/pull/178198