[NFC][AMDGPU] Remove unused TableGen generated enum (#171170)

This GenericEnum was just adding separate values for VOP3P_Pseudo
opcodes in the same namespace as existing opcodes that did not match.
They were defined in AMDGPUGenSearchableTables.inc by tablegen emitter
but were guarded out by #ifdef. Because of that, they were never
included in the code, so the compiler never reported the naming
conflict and the bug never had a chance to surface.

Author: mbrkusanin

llvm/lib/Target/AMDGPU/VOP3PInstructions.td

@@ -1364,16 +1364,10 @@ class WMMAOpcodeMapping<Instruction TwoAddr, Instruction ThreeAddr> {
   field bit is_wmma_xdl;
 }
 
-def WMMAOpcode : GenericEnum {
-  let FilterClass = "VOP3P_Pseudo";
-}
-
 class WMMAMappingTable : GenericTable {
   let FilterClass = "WMMAOpcodeMapping";
   let CppTypeName = "WMMAOpcodeMappingInfo";
   let Fields = ["Opcode2Addr", "Opcode3Addr"];
-  string TypeOf_Opcode2Addr = "WMMAOpcode";
-  string TypeOf_Opcode3Addr = "WMMAOpcode";
 }
 
 def WMMAOpcode2AddrMappingTable : WMMAMappingTable {