[llvm] [NVPTX] support immediate values in st.param instructions (PR #91523)

[Artem Belevich via llvm-commits]

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@@ -2637,25 +2637,49 @@ class LoadParamRegInst<NVPTXRegClass regclass, string opstr> :
                 [(set regclass:$dst, (LoadParam (i32 0), (i32 imm:$b)))]>;
 
 let mayStore = true in {
-  class StoreParamInst<NVPTXRegClass regclass, string opstr> :
+  class StoreParamInstReg<NVPTXRegClass regclass, string opstr> :
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Artem-B wrote:

Down below you have `StoreParamInst` which defines register and immediate store ops. 
`StoreParamInstReg` provides only a register-based store.
I propose to keep instruction definitions within one class only, in `StoreParamInst`, and eliminate `StoreParamInstReg` as redundant.

https://github.com/llvm/llvm-project/pull/91523